The word aperture refers to how large the opening of your lens is. It can be a tricky concept to understand. Aperture is defined by f/stops. The smaller the f/stop number, the larger the opening. The larger the opening, the more light can get in, and the more blurry the background.
Try setting your camera to Aperture priority mode (it's usually indicated by a capital "A" or an "Av." Now, set the f/stop to the lowest number that your lens can go. (Some lenses can go all the way to f/1.2, but most kit lenses only go to about f/3.5.)
You'll want to avoid using your flash for this, so unless you have fantastic window light, try this experiment outside. Once you have your aperture set to the lowest number, try moving in fairly close to a subject, and take the picture. The background should be very blurry. Now, change your aperture to the highest number that your lens will go (most often f/22.) From the same position and angle, take the picture. Notice how much more of the background is in focus - it should be virtually everything.
One more thing to remember about Aperture: If your aperture is set at f/22, the opening is very small, and very little light can get in to hit the image sensor (or film). To allow for a properly exposed photo, the shutter has to stay open for a much longer period. Likewise, if your aperture is set to f/1.8, the opening is very large, and the shutter has to stay open for a much shorter period of time to get a proper exposure.
This photo was taken at f/1.8 at 1/80th of a second. (The shutter was open for 1/80th of a second.) I generally don't like to have my shutter speed at less than 1/60th of a second without a tripod - the photos turn out blurry.



This downloadable set includes:

Line doesn't always have to be straight and well-defined. I took this photo on the Oregon coast during a family vacation in the fall of 2007. To me, the curved lines in the sand, coupled with the diagonal angle of the image, almost creates a feeling of motion. I wanted to try to take a photo that would help me really remember the way that the ocean moved up along the shore, and back again.











