Canonical quantization is a rather formal way to turn a classical
(non-quantum) particle or field theory into a corresponding quantum
theory. It is useful, if you don't have an intuitive picture of precisely
how the quantum theory should work. First you write a Lagrangian for the
classical theory, choose the dynamical variables, work out the canonical
momenta for those variables, turn the variables and momenta into
operators, then impose commutation relations for the operators to account for
quantum fuzziness.