Explain Gray’s model of approach/avoidance motivation. PLEASE HELP!

Read widely and then write your own summary. Make sure you don't copy anything. This explanation needs to be in your own words.

http://www.google.com/search?rlz=1C1GGGE_enUS379US379&ix=sea&sourceid=chrome&ie=UTF-8&q=Gray%E2%80%99s+model+of+approach%2Favoidance+motivation