.BSA File Extension
File TypeBethesda Softworks Archive
What is a BSA file?
Compressed game data archive used by Bethesda Softworks video games; contains 3d models, textures, sounds, and other data referenced by each game.
BSA files are not meant to be altered, but they can be "modded" in order to change the gameplay. Various programs exist to unpack and alter BSA files.