TeX or LaTeX is actually a typesetting system with a built-in macro language. TeX was developed by Donald E. Knuth primarily for books with mathematical content. To create a text, you use various commands, which usually begin with "\". 

TeX is most commonly used with the LaTeX software package. 

An add on programm to LaTeX is pdfTeX, which creates pdf files directly and is used in most LaTeX versions. 

If all the editing is done and the finished document should be saved and stored one should compile it as a pdf, if the ability to further edit the document is desired one should save the document as a .tex file. 

A .tex file can be opened with most of the common text editors. However, it is recommended to use an editor that supports syntax highlighting, so that you can find your way around the TeX commands better. 


- the plain text document can be opened with any text editor

- the layout in a.tex file can be changed and edited


- to see the finshed layout, the file must first be compiled.

- without compiling the .tex commands are visible, which means a worse readability