The role of a User will determine what the user can and cannot do within the app. You edit a user's role by navigating to Settings -> Users & Roles then finding the user you would like to edit and clicking Edit.
A Campaign Manager can edit all segments and campaigns, but does not have access to the account settings of your company account.
An Analyst can read all campaigns and segments, but can't edit them. This role is meant for users that are interested in performance and reporting, but do not need to set up campaigns or segments themselves.
And Administrator can do everything in the app and has full control over segments, settings and campaigns.