Tivoli Storage Manager, or TSM is backup and recovery software made by IBM. it used to be know as adsm. It is one of the most common enterprise level backup and recovery products and is used by a ton of major corporations. It's major strength is that it uses an internal relational database to manage everything including backup media, devices, file versions and clients. The database also allows TSM to use an incremental forever paradigm so that a file, if it doesn't change, is only backed up once. Policies are set in place determining the number of versions and for how long a version is stored.
The necessary components of TSM are:
A TSM server, which manages the backup media and schedules backups.
A (usually) automated tape library (atl) connected to the server.
Clients to backup. These clients can be desktops, servers, workstations.
There are also modules which allow certain applications, such as microsoft exchange and databases to be backed up without halting the application or database.
While the main strength of TSM is its relational database, its major weakness is that it has a steep learning curve and if the TSM administrator hasn't rtfm'd you'll either lose backups you thought you had or backup up everything forever and run out of tapes.