Yes, the backup is automatic for any computer you install the software on, and set it up to backup those directories. Depending on how much you select for backup, it takes a day or more to get all the files uploaded to the server the first time. After that, everything is kept in sync with the server whenever you create, rename or delete a file in the directories you choose to keep backed up on the server.
You can download the files to any other computer using a web browser.
If you have it installed on multiple computers, there's something called the magic briefcase that you can use to keep files in sync between all the computers you have it installed on. (eg, for bookmarks, etc.)
All this information should be on their web site.
-David