-POW is Proof of work (computer mining) -- actual resources like computing power and energy itself is used.

-POS is Proof of Stake (aka Proof of sacrifice) ... All this is is ownership of the coin.  Some coins like dash and PIVX will use proof of stake to create super nodes which are paid interest (leaving your node open and participating in the network).  With deCRED, you have to participate... you use your coins to buy tickets (to vote)... those tickets get locked up until they randomly called by the network (can take 1 to 6 months)... once they are called, it votes and your coins are unlocked with some interest (extra coin).