My brother-in-law called about a bail hearing and I had no idea how to explain sureties

http://www.haddadtrialbook.com/home-page/2013/8/2/haddad-to-resign-after-decade-on-the-bench-in-cook-county.html

My brother-in-law sent a message about a bail hearing and I had no idea how to explain sureties, we panicked through questions until a friend finally found info online.