If you do something that violates the terms of your bond, the prosecution can file a motion alleging a violation, at which point the defendedant can admit to the violation or deny and request a hearing. Then there's an evidentiary hearing, basically a mini-trial, where the judge hears evidence and determines if there was a violation. If that happens, the consequences can depend. You can forfeit your bond, your bond can be raised, new bond conditions can be imposed, etc.
If you were given a cash bond and can't afford it, you can contract with a bail bondsman. That bail bondsman will pay the bail for you, and in some sense takes responsibility for you not violating your bond, in exchange for some fee (usually 10% of the bond amount). That amount is NOT refunded