Depends on the country, but usually a “background check” is nothing more than paying a lawyer to check if you have ever been convicted, accused or investigated for a crime. Prosecutors have an archive and a office of records to collect and share that public information. This is why clearing records are important in courts and settlements. It’s a big mark to say the person is actually alright and won’t be found in the records if searched, as they were cleared. Other than that it is usually just a phone call to a previous employer to ask if you were an asshole there.
Brain uses expectations to decide what to fill perception with. you don’t expect hands to be the same red tone as cola cans.