TeX is a popular typesetting system for authoring technical documents and, in particular, math expressions. There are many implementations of TeX such as LaTeX which is used in academia for typesetting books and papers. This website uses KaTeX for typesetting math expressions.

As opposed to WYSIWYG (what you see is what you get) editors, TeX editors take in plain text as input and render the output. For example, the plain text below is passed to the typesetting system as input.


This input is then rendered to the following math expression.

Regardless of your skill level with typesetting math, I highly recommend checking out the tool MathPix to speed up your workflow.