(written from a Production point of view)
The CBS Corporation was formerly known as Viacom. Following Viacom's split with CBS in 2005, Viacom dissolved and was re-established as the CBS Corporation. CBS acquired the rights to Viacom's Paramount Television, which was subsequently renamed CBS Paramount Network Television (now known as CBS Television Studios) and to UPN which subsequently merged with The WB to become The CW. CBS Corporation also continues to own Simon and Schuster and Paramount Parks, which previously fell under Viacom.
CBS Corporation and the new Viacom are both controlled by National Amusements.