Aperture

A lens's aperture determines how much light it lets through. More often than not, a wider aperture (lower f-number) is preferable, as it will allow you to take photos indoors and in other situations with little or no natural light.

Wide aperture also allows you to use a faster shutter speed, which is important when photographing fast-moving subjects.

The down-side of having a wide aperture is the cost - lenses with wider apertures can cost significantly more than a normal lens.

Slow Sync Flash photography. 

Slow sync flash photography is a simple but very effective way to create a dramatic image. basically slow sync flash photography is using your flash whilst having a slow shutter speed. This will keep your subject in focus but yet capturing a motion in the image, also it picks up any dark shadows in the background.      

                                   

With a normal image, the shutter is open for a few seconds, so the flash is using most of your exposure but with a long exposure your camera's shutter is open for longer than your flash.