calculus 1 is mostly about rates of change, limits, differentiation and applications of differentiation, and maybe a little integration depending on your school. it is of course, in single variable
calculus 2 is mostly about integration and applications of integration. again, in single variable.
calculus 3 is all of the above, except you do it in multivariable. that is, you are working in 3 dimensions or more. you would also do some things about series
you can find more information about these in the course bulletin for your school