The aperture is one of the most difficult things for new photographers to wrap their head around. The number system seems confusing (smaller number, bigger hole), depth of field, how it affects exposure. It’s a lot to take in all at once.
This five minute animated video from YouTuber Apalapse goes over everything you ever needed to know about your camera lens’s aperture. It goes over some of the issues associated with picking which type of lenses you might want to buy, too.