At the most basic level, dotwork tattoos are tattoos that composed entirely of small dots of ink. This technique, which is often called stippling, produces tattoos that are fantastically detailed with shading effects that can be quite subtle. Instead of broad swathes of color, each dot is clear and distinct, even if it is clustered with many, many other dots.
Dotwork tattoos are most frequently done in black and gray, though this is not a hard and fast rule. Because of the nature of this type of tattoo art, some artist prefer to use the Japanese tebori method for tattoos of this sort. Tebori tattooing involves using hand tools rather than a tattoo machine to insert the ink under the skin.
Dotwork is an excellent choice when you want a very geometric tattoo, as it handles shading and contouring very well.
If you are thinking about getting a dotwork tattoo, it is of the utmost importance to find an artist who is skilled with them. Be prepared for a dotwork tattoo to take longer than a standard tattoo do to its high resolution and details, especially if the tebori method is used.