Providing value for value. It's a way of easily giving back if you find some value or you like something. 

https://value4value.info/

Lightning based "zaps" (aka sats or satoshis) are small divisions of a full Bitcoin. 1 Bitcoin = 100,000,000 sats.

Bitcoin is the hardest money in the world backed by the most powerful worldwide decentralized network. Internet money for everyone, with no central control. Furthest thing from Monopoly money. 🙂 To properly understand it will require some effort on your part (proof of work), but it is worth every minute of time spent.