The Unofficial Patch is a combination of the default Basic Patch which mostly fixes bugs only, and the optional Plus Patch, which is kind of a mod adding various tweaks and implementing a lot of unused content, including new quests, levels, weapons, items, characters, dialogue, graphics, models, sounds and original music! Included are also the optional Patch Extras which feature Player Mods, like shaders suites, as well as Developer Tools, like the Unofficial SDK to mod the game.
The original game was already great and this unofficial patch does a GREAT job at keeping it true to itself while fixing all the details and restoring content. It is the perfect unofficial patch a game could hope for. HUGE thanks to the creators of it. I only wish more games would have received as much love as VTMB through this unofficial patch.