How Messages work.
Private one-to-one chats between members - here's how to start one, what you can send, and how blocking fits in.
💬 Starting a chat
Open anyone's profile and tap MESSAGE. If you've never messaged them before, this opens a fresh conversation; if you have, it takes you straight back to the existing thread. Every conversation you have lives in one list under Messages.
📎 What you can send
Text (up to 2,000 characters) and, optionally, a single photo per message. You can send one or the other, or both together in the same message.
🔔 Unread messages & notifications
Conversations with something new show a dot in your Messages list. If you have push or e-mail notifications turned on in Settings, a new message notifies you there too.
🚫 Blocking from a chat
There's no dedicated block button inside the chat itself - tap their name at the top of the conversation to reach their profile, and block them from there. See How blocking works for exactly what that does to your message history.