Regular housekeeping and cleaning is important both privately and at work to have an environment you feel comfortable in and to avoid looking too much for things you need. When it comes to Microsoft Teams, you may find that you have too many Teams to keep track of and that the list of Teams is too long? Maybe some of them are no longer active? Then it is a good idea to archive the inactive teams.
When you archive a team, you keep it for reference, and it is also possible to activate it again in the future should the need arise. When archiving, the conversations / posts and files in the team becomes read-only. You will still be able to search through what you need and you can even keep the team as a favorite. (Worth knowing is that only team owners can archive and restore it. Here you can read about how team archiving works.