Create and Edit a contact
When you open the People app in Office 365, besides working with individual contacts there are two other 'people elements' that you may find yourself working with, or at least working with. These are Contact Lists and Groups.
Office 365 Contact Lists are lists of individual email addresses linked by a shared list name and allows you to pick this list name when sending an email, saving you the time of adding lots of separate individual email addresses. In the past these might have been called personal distribution groups.
If you'd like to know more about how to work with Contacts and Contact Lists in Office 365, then please see the following Microsoft article:
Groups in Office 365 let you choose a set of people that you wish to collaborate with and easily set up a collection of resources for those people to share. Resources such as a shared Outlook inbox (i.e. a group e-mail address), shared calendar or a document library for collaborating on files. Groups are a fundamental sharing feature in Office 365 and are used in different areas of the service, such as SharePoint or Teams, to provide sharing and collaboration.
If you would like to learn more about Office 365 Groups please see the following Microsft article: