You can use lists to determine the type of content contact should receive. For example, you can create lists like Monthly Newsletters, Promotions, Product Announcements, and send relevant emails to list subscribers.
Difference between Lists and Tags
Lists provide better tooling to manage the type of content a contact can receive.
Contact can opt-in to specific lists when they modify communication preferences. Communication preferences link can be shown along with an unsubscribe link under email footer.
Bulk Add/Remove Contacts to List
You can upload CSV file with a single email column to bulk add/remove contacts from a list.
Go to contact lists page. Select list and click Upload CSV.
Specify if you want to Add Contacts or Remove Contacts. Attach CSV file with single email column and click Upload.
Keep in mind that CSV upload will only add/remove existing contacts from list. It will not create new contacts and will skip suppressed contacts.
List in Workflows
Lists can be used triggers to start a workflow whenever a contact is added. There's also workflow action that allows you to add/remove contacts from lists.