I'm new and I really don't know what's Goolge API and for what can I use it. Can somebody explain to me? Thanks in advance!
It is the approved way by Google to make multiple queries. There is lots of info here: http://www.google.com/apis/ If you are asking because the keyword tracker and Coop Network ask for it, all you need to do is go to that url and request one. Once it arrives in your inbox, just cut and paste it into the control panels of the tool you are using.
You can read more here also: http://news.com.com/Google+courts+open-source+developers/2100-1032_3-5623534.html?tag=html.alert