Workspaces are areas where users can upload and handle documents. You can use workspaces to keep your projects or tasks separate e.g. you could have a workspace for documents related to a given client or project, and restrict access to the appropriate people.
Within the Workspace there are folders and documents. When creating a Workspace you have the option to use a template. Templates are predefined Workspaces with Folders, Documents, Groups and Users already populated for use. Templates are designed to save users time setting them up for tasks or projects that are similar of repetitive.
They will be asked to sign up and create a password before they can access your workspace, but they won't have any workspaces of their own. Like anyone else, they can create a free account if they want to start their own workspaces.
Sign up for an account; create a workspace for storing documents; upload a document; highlight text to add a comment; share your workspace with other people to let them add their feedback. The QuickStart section of the user guide should help you get started.