What is a distribution group?
Use Office 365 distribution groups (a.k.a., distribution lists) to send emails or meeting requests to multiple people (for example, a project team or committee), without having to add all the email addresses each time.
You don't need to be an admin to create a distribution group, however if you want people from outside your organization to become a member of your distribution group, an admin will need to set permissions for these contacts. For external contacts from other domains to become members of a distribution group, the admin must make the external contacts shared contacts.
It's worth mentioning that Microsoft now has Office 365 groups, which contain distribution groups, but also include other group-related collaboration features, such as a library for storing and working on group files and folders, a tool for organizing and assigning tasks, and getting updates on project progress. Learn more about Office 365 Groups from Microsoft.