What is a police clearance?

As per the USCIS, the term "police clearance" means official evidence of a record of arrests, lack of arrests, or confirmation that an arrest did not result in court action from a local police department or from a state agency responsible for maintaining arrest records. CITATION:Pg2:section 8; http://www.uscis.gov/sites/default/files/files/pressrelease/natznq2.pdf