From Better Practices

Individuals that use TeX (or any of its derivatives) to typeset their documents generally take extra measures to ensure paramount visual quality. Such documents often contain mathematical expressions and graphics to accompany the text. TeX was not designed for creating graphics; however, certain add-on packages can be used to create modest figures. Because of their scalability, Encapsulated PostScript (EPS) graphics are one of the most common types of graphics used with TeX.

[edit] What is MetaPost?

MetaPost is a powerful graphics language based on Knuth's METAFONT, but with PostScript output and facilities for including typeset text