If you leave a team, that team will be removed from your conversation list. If the team is public, you can rejoin that team at any time. However, if the team is private, you will need to receive an invite from an existing team member in order to rejoin that team. 
 
It’s also important to note that when you leave that team, that team does not lose the conversation history that you’ve contributed, even if you were the original creator of that team. 
 
Also note that if you’re the only admin of that team, you will be unable to leave that team until you assign another member as an admin. 

Leaving a team for desktop or web

If you’d like to leave a team in the desktop and web app, you can do so by following these steps:
1. Navigate to Message via the left-hand navigation bar
2. Select the team you’d like to leave from the conversation list
3. Click on the More kabob icon in the top right-hand corner of the team header bar
4. Select Leave team from the dropdown menu

Leaving a team for mobile

If you’d like to leave a team in the mobile app, you can do so by following these steps:
1. Navigate to Message via the bottom menu bar
2. Select the team you wish to leave under the Teams tab
3. Open the team’s profile by tapping on its name located at the top of the message thread
4. Tap the gear icon in the top right corner
5. Tap Leave team at the bottom
6. Tap Leave in the modal window