Answer:
A line integral is a simple integral.
they look like:
integral x=a to b of (f(x)).
A surface integral is an integral of two variables.
they look like:
integral x=a to b, y=c to d of (f(x,y)).
or
integral x=a to b of (integral y=c to d of (f(x,y))).
The second form is the nested form. A pair of line integrals, one inside the other. This is the easiest way to understand surface integrals, and, normally, solve surface integrals.
A volume integral is an integral of three variables.
they look like:
integral x=a to b, y=c to d, z=e to f of (f(x,y,z)).
or
integral x=a to b of (integral y=c to d of (integral z=e to f of f(x,y,z))).