It basically means this forum now support \LaTeX-markup, which is a popular language in academia used for writing papers. It’s very useful for creating good-looking mathematical/scientific equations. The original \TeX was created by Donald Knuth: a bit of a legend in computer science circles.

Note that the code for the \TeX-logo in \TeX is simply \TeX. So writing $\TeX$ in your messages on this forum, now displays it accurately.

I’ve always found this editor to be a nice way to learn some \TeX in an exploratory way: