LaTeX (pronounced "lay-tech") is a software that is a document preparation system. It is often used to create technical and scientific documents but can be used to create a variety of documents from any field.
Some key features of LaTeX include:
There are a variety of packages available for almost any typesetting need.
Documents can be saved as PDF or PS documents.
LaTeX is accessible online through an application called Overleaf, but can also be installed locally using a variety of open-source packages such as MikTeX.