A more thorough explanation:

A presumption is a legal assumption that must be made based on certain facts. In most cases, these assumptions can be challenged or disproven with evidence. However, some presumptions are considered to be true without any opportunity for rebuttal.

• Presumption of innocence: In criminal cases, the defendant is presumed innocent until proven guilty beyond a reasonable doubt. This means that the burden of proof is on the prosecution to provide evidence that proves the defendant's guilt.
• Presumption of paternity: In some states, 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 challenged with DNA testing.

These examples illustrate how presumptions work in the legal system. The presumption of innocence means that the prosecution must provide evidence to prove the defendant's guilt, rather than the defendant having to prove their innocence. The presumption of paternity means that a man is assumed to be the father of a child if he is married to the mother, but this assumption can be challenged with scientific evidence.