Aperture, what is that?
The aperture is an opening inside the lens of your camera. This opening is adjustable and its size determines the amount of light that goes through the lens when you push the shutter release. It not only controls the amount of light, but also how much of the image is in sharp focus- this is called depth of field.
The size of this hole, the aperture, is described by a number- the aperture value, also known as an F-stop. But the confusing part is- the smaller the number, the larger is the lens opening.
The large lens opening (with the small number), leaves less in focus and gives a shallow depth of field. When you use a higher f-stop value, you will have a small lens opening with more in focus.
So what Aperture do I want to use?
If you look at your lens you will most likely see the maximum aperture the lens can do. This varies from lens to lens, but usually better quality (and more expensive) lenses has a lower aperture value, such as f/1.4 which means they can give a shallow depth of field. It also means that you can use a quicker shutter speed, and shoot in lower light situations, but that´s a topic for another post.
A low f-stop will keep focus on the subject and I like to use that for people and specific details. I prefer a high f-stop for landscapes and macros where I want to preserve a lot of detail.
Give it a try yourself by setting your camera to aperture priority mode and see how your image changes when you try different f-stop values. And if you´re feeling very daring you can try out manual mode as well.
Good luck and feel free to ask questions!