How to do 2d Mode

I heard it is possible to do 2D mode in Opengl, is it true? If yes how may I do something in 2D mode?

Thanks in advance!

i know its hard to believe, but it is indeed possible. check out the redbook:
http://www.parallab.uib.no/SGI_bookshelves/SGI_Developer/books/OpenGL_PG/sgi_html/ch04.html