A patent is a grant of exclusive rights to an inventor for his specific invention. The duration of patents is typically twenty years. Note that a patent is a right to exclusivity. This means that it grants the right to stop others from making, using or selling a patented invention rather than the right to make, use or sell an invention yourself. This exclusivity property of the patent comes into particular importance when the invention is not a self-contained invention, but rather an improvement on top of someone else's invention. The original invention may still be covered by another's patent. Here you have the option to exclude others, and therefore charge others, for the use of your particular improvement. Patents are generally enforced via civil lawsuits. Patent laws are governed by both national and international laws. But, the World Trade Organization (WTO) is actively working to harmonize the national patent laws into a homogenized international agreement.
A trade secret, on the other hand, refers to a particular formula, design or method. Trade secrets are generally protected by not disclosing the information to anyone else and keeping the information private. Here, the owner may make use of other laws surrounding non-disclosure agreements to keep employees from divulging his trade secrets. As of May 2013, the United States adopted the Uniform Trade Secrets Act (UTSA). This act makes it illegal to misappropriate trade secrets for the purposes of either commercial, economic or political (foreign) reasons.