Part of my journey to become a better photographer is to teach myself starting with the basics. I learnt about photography almost backwards. Learning to edit before really getting into the actual photo taking. Read through my notes and see my practice shots while I try to become a better photographer.
What is it?
The aperture is the opening of the lens diaphragm which lets a certain amount of light into your camera. Aperture is calibrated in f/stops generally between f/16 to f/1.4.
How to set it?
The lower the number in the f/stop (ie. f/1.4) the larger the opening in the lens. A large opening creates less depth of field which will give you a blurrier back and fore ground around your subject. This is referred to as Bokeh. The higher the f/stops (ie. f/16) the smaller the opening in the lens. A small opening will give you less depth of field which will give your back and fore ground a sharper look.
When to adjust it?
Use a low f/stop setting when you would like to achieve a lot of blurriness (bokeh) around your subject such as in portraits. Use a higher f/stop setting when taking a landscape where you want everything in focus.
Hopefully this quick overview of aperture basics will help you be able to control your DSLR a little bit better.
See more Photography Basics here.
**This is only my conclusion based on my own research and practices. Everyone has their own processes.**