There are many clamp shapes and sizes on the market, what works best for you depends on what you need them for. Some clamp tools are permanent, meant to be applied and left along for as long as the clamp will hold tension. An example of a permanent clamp is the hose clamp, a device used to attach a hose to a fitting and form a seal. It's applied, and left alone once the seal is established.
Temporary clamps are the ones most likely to be used in a do-it-yourself project or home improvement situation. The bar clamp is a good example; it's used to hold pieces of wood together to facilitate gluing. Another type of temporary clamp is the spring clamp, used for holding a piece of trim motionless on the cutting table, or temporarily hanging unconnected wiring or cables in high places.