Dots are usually die chips. They are small chips at different locations that become points (dots) on the coin.
These marks are an indication of the deterioration of die caused by metal fatigue. The 1-cent 1947 dot is a well-known example. These die chips may be due to the quality of steel in the area, loss of small pieces of chrome on the die during the process of striking or default during the process of chroming.
It was in 1942-44 that the first coins were chromed. Then, from 1945, all the dies were chromed to extend the useful life.
Occasionally, dots can come from gas bubbles (air or other) smaller or larger (pictures below), trapped in the metal. Compressed gases rise in temperature dramatically when striking and they expendent.
On right, 1 cent 1964