An Artificial Star is a point source of light. It is used to simulate a real star indoors, so you can collimate your telescope's optics indoors and/or during daylight.
Commercial artificial stars, such as this Hubble Optics one, cost $25 or more, and their main feature is a small plate that has precision holes of 50 micron up to 250 microns.
You can make your own artificial star, which is very close in function to the commercial ones.
You can watch this short 4 minute video on how I did it, and read on for detailed instructions.