It’s not something Spock and Kirk use to transport themselves through space and time . An intervalometer is really a device you should have if you want to get creative with photography.  This gizmo allows you to program the shutter on your camera to take an infinite number of shots at set intervals in order to produce time lapse videos, a series of action photos, stacked photos used in star trail images or depth of field stacking.  And what ever else you can imagine. For time lapse videos, I may take a series of 500 photos at an interval of 2 seconds.  Yes, you may have to wait patiently for a few hours. The interval depends  on what is happening in your frame and the light conditions.  Clouds moving quickly through a bright sky should be shot in short intervals of a second or two. You will have to set your camera’s exposure beforehand . You combine these images (Shoot in jpegs) in a software program that will make a video for you.  I use Adobe’s Lightroom to make my videos and can alter the length and add music.  I purchased this Satechi model ($59)for a Canon camera at half the price of Canon’s model and it works great!  http://www.satechi.net/index.php/satechi-wtr-a-wireless-timer-remote-control-shutter

The Satechi unit attaches to your hot shoe and the programmable timer is wireless. Both pieces are battery operated.  Below is a sample of a time lapse video I produced with the intervalometer through Lightroom and a star trail photo.