If you're planning on patenting your idea, you should be careful in choosing which patent you apply for when protecting your inventions. There are many different kinds of patents, but most likely, you'll be wanting to choose between a utility or design patent.
A design patent lasts for 14 years. This is subject to change, as are most laws. Design patents are mostly used for, well, designs! If you're an architect and come up with a novel design for a new kind of Titanic that can't be sunk, with unique features that no other ship currently possesses – then you should apply for a design patent. The design patent makes it illegal for anyone else but yourself to replicate your design, sell it, or use it for the whole fourteen years.
A utility patent lasts for 20 years. This is subject to change, just like the design patent. Utility patents are meant for inventions – so you're trying to protect the actual mechanism of an invention. Utility patents protect the mechanism of the invention and its function, but it poorly protects its design.
You might make a dangerous error in choosing between design and utility if you don't seek expert advice. For example, if you make a new rocket-powered vehicle, but apply for a design patent, the only thing protected is the way your rocket-powered vehicle superficially looks. So if you made a red car with twin rockets, with aesthetic “wings” near the doors, the design patent would stop people from making cars with that design: they can't make cars with twin rockets, and wings on the doors. However, because you only have a design patent, anyone is free to make their own rocket-powered car using your idea—so they could make a blue car, no wings, and mini rockets near the tires, and the patent wouldn't make it illegal. If you chose a utility patent, it would be illegal for them to make any kind of rocket car that uses your methods.