For those unaware of the difference, everyone in prison has been found guilty and sentenced for a crime, jail is typically where people are incarcerated before being tried and/or sentenced.

An officer can literally arrest you on whatever charges they might make up on the spot and take you to jail, and depending on a number of specifics you may simply not have many options to leave jail before your trial which is often many months later. I think there’s some form of protection against this sometimes but I’m not well versed enough on the subject to know for sure and make a general statement