Why do you get a period while on BC?

Sa
From what I understand, ovulation is when an egg leaves your ovary and travels down into your uterus where it patiently awaits a sperm to fertilize it. If it's not fertilized, the egg along with the uterine lining is shed during your period.
How then, does birth control work? Doesnt it make you not ovulate so there is no egg to fertilize? If that's the case, why do you still get a period while on birth control?
I've been on birth control for several months now, and I JUST NOW realized that I don't understand this! 😑