Auto-flash goes off automatically if there isn't enough light or when the light is coming from behind the subject. They allow for better centering of your subject as well as using fewer batteries than a preview screen. Preview screens are small LCD color displays built right into the camera. There are many additional options that are available. Burst mode lets you take one photo after another as long as you hold down the shutter button.
Time lapse takes a series of pictures at specified intervals.
This is very nice for botanical shots. Auto-exposure calculates the correct exposure for the scene. Automatic white balance adjusts the colors in the image to match the source of light. Auto-advance prepares the camera for the next photo. A very important accessory is rechargeable batteries.