Aperture and depth of field

So many people look at the aperture number, or depending on what camera you have the picture to help understand what f-number means more or less light.  What most people don't think about, especially those new to photography, is how the aperture effects the depth of field.  I know in my early photography days I mostly left my f-number as low as I could so that it would let in the most light possible, however depending in the picture you're taking that might not be the best option.  Generally when aperture is mentioned it's mentioned in combination with how aperture, ISO, and shutter speed effect the outcome of a picture.  This is extremely important because when you change your aperture you are going to have to change the others also to compensate.

When using a lower f-number your depth of field is smaller.  You will have less in focus, and what is blurred will be at a higher blur than if you have a larger f-number.  As your f-number goes up so does your depth of field, however, as your f-number goes up the amount of light allowed in is smaller. 

I know I'm not the best at understanding through writing.  I am more visual to really understand what I read, so I am including three different pictures to show the difference in depth of field as the f-number increases.  I am only focusing on the aperture in these pictures, so I will not be posting the shutter speed and ISO settings.  I want you to really focus on what the aperture does to the depth of field. 

Notice with the top picture my f-number was 1.8.  This means my aperture was completely open allowing in as much light as this lens allowed.  It's pretty obvious that at this level the amount of blur is very high.  As you change your f-number the blurring lessens.  The second picture has an f-number of 8.0 still blurring the background but leaving more of the foreground in focus.  Also the background isn't as blurry as the top picture.  The bottom picture was taken with an f-number of 22.0 which was the highest number this lens allowed.  This means the aperture is almost all the way closed letting in very little light, but if you notice most of the picture is in focus.  This gives a much greater depth of field. 

Well that's my breakdown of how aperture effects the depth of field in a photograph.  I hope this was broken down and easy to follow how it works.