You can send a "Zap" or Lightning tip to anyone. To have it be counted as a Zap and not just another Lightning tip, the receiver needs to use one of the following wallets:

strike.army
vida.page
stacker.news
Bitcoin Jungle
ln.tips (LightningTipBot)
Geyser
Bitcoin Beach
Current (Client+Wallet)
Wallet of Satoshi

Zaps are just Lightning tips that are integrated to Nostr and are displayed on Nostr posts and profiles.