Zaps are how you send tips to people. They use the bitcoin lightning network. Each app differs slightly in how they’re implemented in the UI. I see your Primal address, so if you’re using their built in wallet then everything is right there in the app. When you send a zap you can customize the amount and include a message. You can zap directly on a post and it will show on that post. Or you can zap someone from their profile and it will just go to their wallet, but won’t show on a specific post.