Being a manager means that you have full control of a workspace.
- View, modify and delete any item in the workspace.
- Change the settings of the workspace.
- Create teams and assign people to them to control permissions.
- Control the membership by inviting and removing people.
- See the recycle bin and restore deleted items.
A workspace can have as many managers as you like; all of them will have equal powers.
Manager rights are specific to a workspace - you can be a manager of one workspace but a normal member of another.
Not sure if you're a workspace manager? If you are, you will see the Manage Workspace cogwheel icon at the top of the page.