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.