In Outlook on the web, you use the People page to view, find, create, edit, and delete contacts. You can use your contacts for your own reference, and you can automatically add them as recipients when you compose an email message. You can also have instant access to see who someone is and how you know them, be able to quickly get content related to one of your contacts without leaving your current task, and hover over anyone's name in an email message or calendar item to show their contact card.
People is where your personal contacts are stored and where you can view any address books that have been set up for your organization. People is a way that Outlook on the web can help you get to the most important messages first. People works in the background to determine who you correspond with the most, and shows you how many unread messages you have from those people.
Note: If you are looking for information on different distribution groups UW-Madison currently offers, read here: Office 365 - What are the differences between an Office 365 Group, an Office 365 Security Group, a Contact list, a Google Group, and WiscLists?.
The first time you view People after you receive the new experience, you can choose a new view of People and pin that view so it's the first thing you see. You can change your pinned view at any time. You can choose from five default pinned views:
To pin a view, just choose the Pin this view button next to the view you prefer. You can also access each one of these views by choosing the view in the left pane under Featured people.
Once you've set up the view you want in People, you can use the following documentation to help get you started on working with contacts, contact lists, and contact folders:
For more information about using People to manage your contacts, read here: Using contacts (People) in Outlook on the web.