I don’t really understand - I was asked to sign a work contract with a rule about keeping information secret. After I leave this company, I have to promise not to share the information I learned and...

Like Kat said, it is a common practice for companies to want to keep certain information propriety. It's like restaurants or food companies not... wanting to share their "secret" recipes to prevent competition. They typically do not prevent you from using skills or general knowledge gained at a company. You can also think about it like plagiarism. You learn you how write essays or research papers, but schools do not want you to just copy and paste the work of others. I also encourage you to read it thoroughly and understand what limitations are being placed on you. Non-compete clause especially can be hairy as they may attempt to limit your ability leave and go work for a competitor or open your own business doing the same job. Usually there is a distance associated and/or a time limit. These are more an attempt to prevent employees from leaving and taking clients away from a business. The ability to enforce them is also different depending on the State or Country that you are in. more