LaTeX is a markup language for describing a document. It can also be defined as a document preparation system. LaTeX is mainly used to create technical or scientific articles, papers, reports, books or Ph.D. thesis.

There are a number of LaTeX distributions you can install on Ubuntu. One such distribution is TeX Live.

1. To install Tex Live LaTeX distribution on ubuntu use the following command.

   sudo apt-get install texlive-full  

2. To edit LaTeX documents we need an editor. There are a number of LaTeX editors you can find. I recommend Texmaker, a cross-platform LaTeX editor. To install Texmaker on Ubuntu use following command.

   sudo apt-get install texmaker  

3. To open Texmaker on Ubuntu use following command.

   texmaker  

4. Now let's create a simple document using Texmaker. Click on File -> New and insert following lines in the blank document.

   \documentclass{article}  
   
   \begin{document}  
   
     Hello world!  
   
   \end{document}

5. Now save the document as a 'tex' file by clicking File -> Save. Compile the document clicking the arrow Quick Build.
   

You can learn more about LaTeX by referring to this link.