General data that doesn't have any categorization. This could be due to either internal reasons, or because it simply isn't being tracked categorically.

A cache of HTTP responses.

All the Instances present in memory.

Events, signals, connections, etc.

All of the data in Lua, including everything happening in core scripts, built-in data types, etc.

All memory being manipulated and referenced by scripts.

Collision detection in the Workspace.

Physics bodies and the components that control their behavior.

Rendering solid models (stuff made with Union, Negate, etc.).

Rendering of mesh parts.

Rendering of particles from ParticleEmitters.

Rendering of regular parts.

Spatial hash lookup tables of the game world that are used for rendering.

Rendering of terrain geometry.

Rendering of textures in the game world.

Rendering of texture composition maps that are generated for Humanoids.

Data of sounds in-game.

Playback of sounds in-game.

Occupancy/Material data of the Terrain.

Gui element data and rendering.

Playback of Animations on Humanoids and AnimationControllers.

Pathfinding for Humanoids via the PathfindingService.