MiKTeX (pronounced mick-tech) is an up-to-date implementation of TeX/LaTeX and related programs.
TeX is a typesetting system written by Donald Ervin Knuth who says that it is intended for the creation of beautiful books - and especially for books that contain a lot of mathematics.
It is very easy to install MiKTeX on Windows. The MiKTeX Setup Wizard guides you through the installation process. You don't have to be a computer expert.
On a Mac, you can use the Drag'n'Drop installer to install MiKTeX.
A complete set of additions (programs, styles, fonts, …) are available to help you typeset your documents.
MiKTeX's integrated package manager installs missing components from the Internet, if required. This allows you to keep your TeX installation as minimal as possible (“Just enough TeX”).
MiKTeX Console helps you to keep your TeX system up-to-date by installing the latest package updates.
MiKTeX comes with TeXworks, a TeX frontend which you can use it to edit and preview LaTeX documents.
The MiKTeX package repository is updated regularly.
MiKTeX is open source. You are welcome to redistribute MiKTeX under certain conditions.