Asset bundle
A package of pre-built game resources — models, textures, sounds, prefabs — loaded at runtime instead of being baked into the executable.
The term comes from Unity, where AssetBundle was for years the only way to ship content outside the main build, but the idea is older: Doom had its WAD files and Quake its PAK files. What changed is that bundles now arrive over the network, so a mobile game can download a new level without going back through app store review.
The trouble is dependencies. If two bundles use the same texture and neither marks it as shared, it ends up in both — and in memory twice. Unity's answer was the Addressables system around 2018, which handles dependencies and addressing on top of the same bundle format. The rule of thumb has not changed: a good bundle is a set of things that get loaded and thrown away together.