Occam's razor

Occam's razor is a guiding principle to verify a hypothesis, to propose a theory, to solve a problem or to deduce logical conclusions. Other things being equal, simpler explanations are better than the complex ones.  More things should not be used than are necessary. It is a law of briefness that says that it is not worth it to do with more what is done with less.

Ockham was a town in England. William of Ockham was an early 15th century English theologian and philosopher. Jis original words are "plurality must never be posited without necessity". Razor was referred to shaving away unneeded assumptions to prove a hypothesis. It is a tool to encourage parsimony in argument or simplicity in logic. It says that simplest explanation is usually the right one.

It is used in many number of fields in science, medicine, logic, mathematics, philosophy, theology and law. It can also be used in context of simple things and observations in every day life. It helps in reasoning to slice through the problem or situation. If you find a fallen tree, most possible claim to verify first is that some wind would have blown it down rather than some meteorite hit it which requires several other rare things to happen.

References
Wikipedia Occam's razor
HowStuffWorks Occam's razor