It is about sharing expertise at Google Co-op.
Here Google invites you to share informationon different topics and mark/add pages which you think, are relevant to some topic.
As a user, you can subscribe to different services and then include them in Google search, more precisely, Personalized Google search in oredr to get more exact search results.
Google Trends is about knowing, what rest of the world is searching.
You enter a keywod in search box, click on search trends and you are presented with a graph of search volumes. I entered Punjab, and got a graph like this plus the stats of searches about cities/regions/languages of Punjab. Also some pertinent news resuls are also displayed. Quite useful to know, how valuable your search is.