... as newsletter tool
You would like to occasionally send out information about news, events, circular mails, etc. and don’t want to manage the newsletter subscriptions? That is the classic area for a mailing list.
The list can be set up such that those who are interested can subscribe and unsubscribe themselves. The author simply sends the newsletter to the list, which does the rest.
... as a discussion platform
On a discussion list, the participants discuss a certain topic. Here, every member can send a message to the list that then goes to everyone. These kinds of mailings lists can improve internal communication in a working group, for example.