What Is Aperture?

Aperture is the size of the opening in the lens when a photo is taken, which is measured in f-stops.

Source: engadgenet.com

According to Digital Photography School...

A large aperture allows a lot more light to fall onto the sensor, and when this happens you have the freedom of using a faster shutter speed. This is especially handy in situations of low light and fast movement, such as indoor sports or a water fall at the end of the day. That’s why larger apertures and fast action shots indoors need to go hand in hand. By widening your aperture you have a better chance of the movement being “frozen” in time and the camera won’t have time to think about camera shake. If done right, you’ll find good sharp images of freeze frame shots without any blur at all.

In your digital photography you should also know that also a large aperture can give you a crisp depth of field. It gives you the opportunity to have your background out of focus giving you clearer focus for the subject close up. (You should always use macro lenses for very, very short depth of field because you get more clarity and sharpness. You can get in closer too, without the subject blurring as it would have without the macro lens.) Portrait photography works well this way.

On the other hand, a small aperture in your digital photography gives you the opportunity to get a slower shutter speed because once light is reduced onto the sensor, the shutter speed will respond.

To illustrate how aperture affects depth of field:

I had to change my ISO from 500 to 2000 to maintain the correct exposure.  My shutter speed went from 1/3200 of a sec to 1/60.

What depth of field is your comfort zone?  What types of shots do you love to take?