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

https://www.torontomike.com/2021/01/what-to-do-if-youve-been-charged-with-a-probation-violation/

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