What is the meaning of specification of 1/2,3/8 and 1/4?

Electric drill and impact wrench have a specification data of 1/2,3/8 and 1/4,do you know what is the meaning?

It is the size of the socket wrench.

The difference between a 1/2 size socket wrench and a 3/4 size socket wrench is the difference in size. The size of the sleeve is metric, generally 1/4 head, 3/8 head, 1/2 head means that the sleeve is a square mouth. Among them, 1/2 head = 12.5 mm, 3/8 head = 10 mm, and 1/4 head = 6.3 mm.