If you have a large Drupal site, you may have a large number of roles and users.

• How do you know if a role is set up correct?
• How you know if a user has the correct permissions?

Yes, you can create fake accounts for each user role, but that becomes very cumbersome if you have more than a couple of roles.

Yes, you can ask the user for their password, or reset if for them, but that's a painful process.

The solution is the Masquerade module which allows you to easily browse the site through the eyes of any user you choose: