Things They Don't Teach You In Computer Science 
csomar: In school or universities, generally they teach only the thoerical part. The real world scenario is another important part, that everyone discover it himself. It's later called "Experience" and "Career".If you want just to be an ordinary guy, just take a job. Most luckily, you won't need to know much about finance, business... you'll just do what they want you to do.However if you want to build your startup yourself or start a company and be the leader, then you need knowledge. You don't really need deep knowledge on Marketing, but just  small ideas to get you started.