A more thorough explanation:

A legal presumption is an inference or assumption that a fact exists based on the known or proven existence of some other fact or group of facts. It is a rule of evidence that calls for a certain result in a given case unless the adversely affected party overcomes it with other evidence. A presumption shifts the burden of production or persuasion to the opposing party, who can then attempt to overcome the presumption.

For example, in a criminal case, there is a legal presumption that the defendant is innocent until proven guilty. This means that the burden of proof is on the prosecution to prove the defendant's guilt beyond a reasonable doubt. The defendant does not have to prove their innocence.

Another example is the presumption of paternity. If a man is married to a woman when she gives birth, he is presumed to be the father of the child. This presumption can be overcome with evidence that proves he is not the biological father.

Overall, legal presumptions are important in the legal system because they help establish certain facts and shift the burden of proof to the opposing party. However, they can be overcome with other evidence.