BBEdit is not part of the pre-installed Mac software, it is a commercial third-party application: probably the best text editor for Mac OS, and one of the bests of all.

There is also a free version, TextWrangler, that offers a large part of BBEdit features... but dictionaries, one of the most important BBEdit features.

An interesting note: by downloading TextWrangler (free) you can upgrade to BBEdit saving a lot of its cost.