The Archive Chat feature allows you to hide a conversation from your chats screen and access it later, if needed. You can archive group or individual chats to better organize your conversations.
Note: Using Archive Chat does not delete the chat or back it up to your phone's memory.
The chat is now archived and will not appear on your chats screen.
You can archive all chats at once by tapping More > settings > chats and calls > archive all > yes.
Archived chats will also reappear when you receive a new message in that conversation.