A Pterygium is a raised, cream colored growth usually on the nasal side of the white of the eye. They sometimes get yellowish or reddish. Before the growth extends onto the cornea it's called a Pingueculae. When it extends onto the cornea it's called a Pterygium.
Pterygiums are usually caused by dry, hot, windy environments, and are found often on people that spend a lot of time outside. A Ptergium is not dangerous and it is not cancer, but can become uncomfortable. The main problem is that they can eventually distort vision due to the fact that they can grow onto the cornea, and eventually even onto the central part of the eye blocking light from entering.