The typical cabochon has a flat back and a domed top. Cabochons are usually glued into settings to make pendants, rings and bracelets. Examples are shown at

http://www.uq.net.au/~zzlstein/rocks/rockindex.html

Keen lapidarists make fancy cabochons of many and varies shapes. Examples are shown at

http://www.uq.net.au/~zzlstein/gatton/fancy/fancycab1.htm