Team admins can sign in to the account of anyone on their team. Team admins can access different team member accounts to:
Note: If a team member linked their personal and team account, “sign in as a user” doesn’t give admins access to that team member’s linked personal account. However, admins can view the name and email address of the team member’s linked personal account.
You'll then be taken to the account of the user you selected, where you can act on this user's behalf. When you're done, be sure to click Sign out on the red banner at the top of the page. This will help you avoid accidentally making changes to the wrong account later.
If you use sign in as user to access a team member's account, you will have the option to notify your team member that you have accessed their account.
Team member / admin notifications
If you click Change notification settings in the notifications window, you will have the option to select who receives a notification that you have signed in as a team member. These options will vary slightly, depending upon whether your account has one or multiple team admins. If you select The member and activity log (recommended), the team member will receive an email notification that you have accessed their account.
Any use of sign in as user and any subsequent actions you take on behalf of a team member will be logged in your team activity log.