If you abide by something, you obey or comply with a rule. If you don't abide by the rules at school, you might find yourself in the principal's office.
To accept a rule or act according to a recommendation is to abide by them. If a judge makes a ruling, you have to abide by her decision. If your parents set a curfew, you'll get in trouble if you don't abide by it. This phrase comes from the verb abide, which today means "tolerate," although it originally meant "wait," from a root meaning "remain, wait, or dwell."