I am looking for some help learning about the Gate Nodes

I am looking to learn more about the Gate nodes.  I have tried to look online but I couldn't really find any examples of anything.  I found some info on wikipedia about the over-arching concept of gates for different scripting languages, but I guess I still don't really understand what their purpose is in grasshopper or how they could be implemented.  If anyone would be willing to explain them or possibly post a definition that makes good use of them for anyone interested in learning more about them, that would be greatly appreciated.  Thank you.