Performance/Caching section of the docs isn't clear enough. It says that the default caching mode is CACHE_TRANSIENT, but there's no explanation on what does it actually mean.

Does it mean that all queries are cached using transients? If so then it would be good to mention what is the default cache expiration and what are the implications of transient caching.

In addition to this, I would also include a paragraph explaining how to change the default caching mode using the timber/cache/mode filter.