Activision sends along patches for Call of Duty and Call of Duty: United Offensive, updating the original game to v1.5 and the expansion pack to v1.51. The updates offer new multiplayer and mod features, as well as some singleplayer fixes (United Offensive). You can find the full readme for the COD 1.5 patch here and the readme for the expansion pack here. Here's a bit on the Tigertown MP map that's included

Tigertown is a small farm town located in Normandy, France which has been partially destroyed by a heavy artillery attack. The environment is designed for "Search and Destroy" as the American Airborne forces push their way up the town's hillside to knock out the flak88 and Tiger tank heavily guarded by the German Waffen SS. The Allied forces need to attack strategically and gain ground quickly so as to distract the Axis from properly defending their positions. Precision flanking from both sides is a key factor when taking over and controlling the town.