What are the units for `renderer.info.memory`?

The WebGLRenderer has a property called info that reflects various rendering stats such as render calls and memory use:

What are the units for this memory use? Kb? Mb?

For example, when I call renderer.info.memory.geometries I get: 31.

This is the count of geometries.

Thanks! Out of curiosity, why is it organized under “memory”?