The aperture is the iris of your camera. It controls both how much light gets in your camera and how sharp your photos are. Here is a quick tidbit review of how that works.
F-stop refers to the number you have your aperture set to. A high f-stop (Eg. f22) is a small hole, and a low f-stop (eg. f8) is a big hole. A small hole means that more will be in focus, and less light will get in, while a big hole means that only a small area will be in focus with more light.
Typically a low f-stop is used for portraits and taking photos of single subjects when you don’t care too much about the background, or want a focused image.
A high f-stop is used when you want to see more, like in landscape photography when you want to see more of the background, or even in portraits when the subject’s surroundings matter to the image.
But wait! We forgot the light! For every time you change the aperture, the light getting in is different, so make sure you have your other setting to compensate, and maybe a tripod to make sure you don’t shake when you choose to take a high f-stop photo of that mountain at 8pm.