A warrant is a document that authorizes the government to do certain things. Sometimes a warrant authorizes entry into a closed space such as a house or building. Other warrants authorize the search of a device such a computer or cellular phone. Some warrants are issued to secure the arrest of someone who has violated the law.
Warrants contain affidavits from a law enforcement officer who swears to a specific set of facts. These facts must have probable cause before a judge will sign. For a finding of probable cause, the judge must have a reasonable belief that a crime has or is being committed. It does not take a lot of evidence for a judge to find probable cause. It should be noted that this legal standard is MUCH lower than a jury must find to convict, which is: evidence beyond a reasonable doubt.
Levels of proof chart: The following chart is helpful in explaining the levels of proof.