Kinda yeah... They zap you and put their ad in the message.  It's concise.  The one I've received most is for a video service.  Cool.  Though Nostr is 4 years old it's still very very new and the silo of influence is strong so breaking in without ads or connections is tough.  A 21sat zapvertisement is a cheap way to get your message seen and maybe build a platform on the protocol.