What is investment banking?

So my back up plan is being a banker.

From my understanding, we sell companies worth millions and make a cut?

Or

We raise capital for companies?

https://en.wikipedia.org/wiki/Investment_banking

http://www.investopedia.com/articles/personal-finance/042215/what-do-investment-bankers-really-do.asp

Hahaha. Your back up plan. That is like saying Harvard is your safety!