LaTeX compilers can be used online or can be installed on your computer (or mobile device). Instructions for installing a compiler on your computer are beyond the scope of this guide.
See below for some great browser-based compilers.
Browser-based LaTeX compilers are a quick and easy way to get started with typesetting because they don't require downloading/installing.
When you only need to format a few equations, you can use one of these LaTeX equation apps.
These handy apps turn your code into an image file of the typeset equation which you can insert into a document or presentation.
(The equation above was typeset using Tex2Img.)