TeXShop is a very useful tool, a TeX previewer for Mac OS X, written in Cocoa.

Since pdf is a native file format on OS X, TeXShop uses "pdftex" and "pdflatex" rather than "tex" and "latex" to typeset; these programs in the standard teTeX distribution of TeX produce pdf output instead of dvi output.

TeX is a typesetting program by Donald Knuth, used extensively in mathematics, computer science, physics, economics, and other fields.

For a history of the development of TeX, see Just What Is TeX. Consult the TeX Users Group Web Site for additional information.

To use TeXShop, you need to learn TeX or LaTeX.