Occam's razor

Occam's razor tells us a simple explanation with few assumptions is more likely to be true. Something could have happened in several different ways. Then a way with few guesses is more likely to be correct than a way with many guesses. Of course if a complex explanation works better than a simple explanation we take the complex explanation seriously.

Example
One or more trees fell down during a storm, which is more likely? Both could theoretically happen, still we have no evidence: Which explanation do we choose? The first explanation needs several unlikely assumptions all to be true so it's most likely the wrong answer. Occam's razor suggests that the wind blew the trees down. That's the simplest answer and therefore most likely the right one.
 * 1) The storm blew the trees over.
 * 2) A low flying Alien spacecraft knocked them down and afterwards the Space aliens used their superior technology to eliminate all other traces of their visit.
 * 1) That aliens visit the earth
 * 2) That they knock trees down
 * 3) That they remove evidence of their visits.
 * 1) The space alien explanation involves three improbable assumptions.
 * 2) We know that heavy wind sometimes blows trees over.