Within a Workspace (or account) you can have different users. Users are all the people that have access to the Workspace. One user is the owner of the Workspace, and only the owner can add, edit and delete other users. Each user has their own login details.
To view and edit the users, click on the Workspace name in the upper right corner and click on 'Users' in the dropdown menu. You can add a user by clicking on the 'Add new user' button on the Users page.
When you add a new user, an invitation will be sent to the email address of the new user. This invitation will contain a link to set up a new password. Once set up, the users can now also log into the Workspace.
For example, you could have different users within one Workspace if you want multiple people to be able to use the same account. You, as the owner of the Workspace, would be able to invite them and delete them when you want.