LyX - My New Word Processor
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When you create a formal document, you don't just write it any way you want
to; you must follow some rules. For example there are fields that are included
in an article: Title, Author, Date etc. They are supposed to appear in
some order.
TeX is a language designed back in 1978 by Donald Knuth to allow users to
create documents in the right format.
Back in those days text-only terminals were in use, but a dot-matrix printer
could print a postscript file with the right font faces, sizes, weights, etc.
So, it was a popular way to create papers to be submitted that include math
formulae.
TeX is very useful today if you want to embed math in some inetrnet pages.
For example, you can use it to add math formulae to your WordPress blog or to 
insert math formulae in an e-mail message composed and read with Thunderbird.
A more user-friendly way to compose such document - including CV's - is with
the LyX word processor that includes GUI.
Adding a math formula is much easier than writing it directly in TeX:
you simply click the Sigma on the toolbar, and inserting your formula.
you can add symbols using the bottom toolbar then or type TeX keywords,
Expressions can be entered in a more user friendly way then, when you use
the mouse or arrow keys to place letters, numbers and symbols in the write
place.  
While editing, you can view a PDF output by selecting from the menubar:
Document->View PDF.
You can also export file as a PDF document using the file menu. 
If you want TeX files, you can choose LaTeX
While editing, you can view a PDF output by selecting from the menubar:
Document->View PDF.
You can also export file as a PDF document using the file menu. 
If you want TeX files, you can choose LaTeX.

A good place to learn about LaTeX and the order of fields in various types
of document is in https://en.wikibooks.org/wiki/LaTeX