Progressive web apps are said to be a combination of traditional website and a conventional mobile application. In other words, we can say that they are the mobile experiences that integrate the best of the web and the best of the apps. These apps can do almost anything a traditional website can do, and most of the functionalities mobile applications offer. This includes indexing for search engines, push notification, access to common hardware functions, online and offline browsing etc. They are useful to the folks who use a website regularly, that live in a tab, no install required. 
Progressive web apps are more powerful one, loading the data quickly even on flaky networks, sending appropriate push notifications, and even having an icon on the home screen. They are usually built with the progressive enhancement and they work for many consumers irrespective of browser choice. 
The recent advancements in the browser and in the availability of service workers and in the Cache and Push Application Program Interfaces have enabled the web developers to allow the folks to install web apps to their home screen, receive push notifications and even work offline. A service worker is a script which runs in the background and can intercept the network requests and return a cached response. The Service Workers also support push notifications.
The native apps are recommended for the applications that we expect the consumers to return to frequently. A progressive web app for its online check-in process, allows the users to access their tickets without an internet connection. Most of the e-commerce industries use the progressive apps. A progressive web app works in all browsers, and the experienced is increased whenever the consumer’s browser is updated with new and improved features and APIs.
Characteristics of  Progressive Web Apps:
Progressive:
A progressive app works on any device, which takes advantage of any feature available on the customer’s device and browser. 
Discoverable:
Since the progressive app is a website, it should be discoverable in search engines. The major disadvantage of the native apps is that they still lag behind websites in the feature of search ability.  
Linkable:
A well-designed website should use the URL (Uniform Resource Locator) to indicate the current state of the application. This will enable the web app to reload its state when the user shares the app’s URL. 
Responsive:
A progressive web app’s User Interface must fit the device’s form factor and screen size. A progressive web app should be similar to that of a native app and be built on the application shell model with minimal page refreshers. 
Connectivity-independent:
The progressive web apps should have the capability to work in areas of low connectivity and also offline mode. It must be readily available at any time by installing on the device’s home screen.
Re-engage able: The folks are more likely to reuse their apps and these progressive web apps are intended to achieve the same goals through features such as push notifications. 
Safe:
These apps can be hosted over the HTTPS (Hyper Text Transfer Protocol) to prevent the middleman attacks. A progressive web app has more intimate consumers and all the network requests can be intercepted through service workers. When new content is published and an individual is connected to the Internet that content should be made available in the app. 
Advantages of Progressive apps over mobile apps:
Better Performance:
In the present era, the progressive apps are using the latest technologies such as Service Workers to serve WebPages, Efficient content etc.  And also, the entire application is cached locally, allowing for fast access, regardless of network speed. 
Secured Network:
The Progressive apps are served through the TLS (Transport layer Security) connections, which means they are secured towards middle-man attacks, spoofing and other various ways of intercepting HTTP(Hyper Text Transfer protocol) header data like traditional websites. 
Offline Mode:
One of the major advantages is that in progressive web apps there is a possibility of browsing the web pages in online and offline mode. When a user is in online, the content is loaded fast and it is not hindered by a lack of internet. Each and every time the 3G connection has an issue, the websites throw error messages and blank screens. And also in certain situations websites are limited to the internet connectivity. On the other side of flip, the mobile apps are often self-contained, allowing the folks to browse the app when not in online, thus increasing the availability greatly. This works by saving the information the user has already accessed.     
If there is no internet connection, the folks browse to a new web page not previously visited, instead of getting an error screen in the browser, it is possible to show a custom offline page. By allowing the people access to the product catalog in offline mode as well, the enterprises can potentially increase their customer retention and engagement rates dramatically. 
Push notifications:
At the beginning stage, only the mobile apps had the capability of giving notifications to its users. But, now progressive apps also do this job successfully. The marketers and conversion experts prefer push notifications since they are being read and interacted more often than newsletters. And also, by adding the progressive app to the home screen, similar to a mobile app, one can increase the chances of the users re-opening an app enormously. Most of the leading e-commerce business released their progressive app and got a good profit.
Looks like an app - functions like a website:
The progressive apps are known for its features like indexability and the freedom to update with the help of the traditional websites, whenever it is needed. It looks like an app but it functions like a website, allowing for the fast iterations and fixes without waiting. For each and every change in mobile apps, a moderator has to approve the changes before the new version is pushed live into app stores. Like the websites, these apps can be accessed through the URLs and indexable by the search engines. It can be designed to look and feel exactly like the existing corporate website or mobile app, and also they can be purposely different to let the folks know they are browsing progressive web apps. 
Indexable by Search Engines:
The search engines like Google, Bing and other search engines cannot access the data and certainly not provide links to the internal content. But the progressive apps benefits the folks to optimize for keywords, rank on the data similar to that of the normal website.     
Improved Performance:
Progressive Web Apps works significantly faster because of the technology caches and serves text, style sheets, images and other data on the websites. The service worker, which works separately from the website, only requests the raw information and not any layout information. 
Fast install on devices:
The browsers like Chrome, Mozilla prompting the folks to install the progressive web app when the folks are visiting the website. They also add the value in terms of authority and reliability. Compared to the mobile apps, the users install progressive web apps, the visitors are not routed through Google play or the App Store, but directly downloading the app onto their device. 
Author Bio: 
Anand Rajendran is CEO and Co-Founder of <a href="https://www.zoplay.com/">Zoplay.com</a>, best PHP scripts development company located in India. Zoplay is a part of Casperon Technologies a leading social and mobile development company which developed a Zoplay Scripts. I'm a Tech geek, Digital marketing expert, Entrepreneur, and Atheist who loves to write everything about PHP Scripts and mobile application development.