A workspace includes all of your team's data, including leads, customers, labels, quotes, etc.
You might have multiple workspaces in a case that someone outside of your team has invited you to another workspace, and you accepted the invitation.
Workspaces are completely separate from each other. This means that any data that you add to one workspace, will never be shared with other workspaces.
You can switch between workspaces in the Leader's side menu.