LaTeX is a package meant to simplify TeX typesetting. TeX is a programming language meant to typeset documents attractively. There are quite a few TeX / LaTeX editors freely available on the internet. Overleaf, is a widely used online LaTeX Editor.
People who use mathematics in their papers or work will benefit the most. LaTeX has many benefits besides math, including an easy ability to work across different OS and easily managing long documents with heavy graphics. It will also manage footnotes and bibliographies (though not as easily as Word and Endnote).