I am confused with these terms in Adword. Can someone explain this. How can I use this tool efficiently?
Search network expands your searches beyond Google itself. Google partners with some other companies (like AOL), and offers results to them, too. Search network is not a bad thing. Content network is completely different. It's those little ads that you often see on peoples' websites and blogs. Not a good thing to do initially. Turn off this option for now.
The content network is sometimes better than the search network, and sometimes worse. But when you're starting up a campaign, the content network can really confuse the stats, so I often switch it off as well, at least until the search campaign is working...
I think in content network there is high probability of invalid clicks, but it reaches to greater number of audience