This building block allows the administrator to create a valid session as a different user. For the purpose of validating portal customizations or troubleshooting administrators often use multiple accounts to access the system. This method allows the preserve the original password. It is a parallel to the Unix su command. It effectively allows to impersonate another user.
https://github.com/OSCELOT/LoginAs/blob/master/img.php.jpg
The use of LoginAs can be provisioned via a system role or a course. If a deployment is delegated via a course, all members of the course will be able to use LoginAs. The course itself should have at least one content item with the link provided in the system settings for the building block.