English to French Art/Literary Music Livre sur la carrière des Rolling Stones

The Rolling Stones hit the film festival circuit in support of their new picture directed by Martin Scorsese. The group attended the premiers in both Berlin and London in February 2008. The film spawned a soundtrack that was released as a single and double disc. The DVD followed in July. The Stones also signed a new deal with Universal Music Group, the world’s largest music company, to bring their catalog to the label.
**The back catalog** became the focus of most Rolling Stones activities for 2009 and 2010. The 1965 film Charlie is My Darling came out on DVD. Get Yer Ya-Yas Out was re-released as a deluxe four-disc set including previously unreleased tracks and film from the Stones plus sets from B.B. King and Ike and Tina Turner, who opened the New York shows in 1969.

Encore les Rolling Stones...
Cette fois, je bloque sur "back catalog", je n'en comprends pas bien le sens.
Et pourquoi parle-t-on ici d'un "catalog" ? Quelque chose m'échappe.
Merci pour votre aide !