Hybridization is a way to explain molecular shapes that can't be explained easily by considering simple overlap of the s and p orbitals. If only these simple atomic orbitals were involved in bonding, all bond angles would be the same as those between the p orbitals (all 90°).
Hybridization is a mixing of valence atomic orbitals to give a new set of orbitals that reflect the (correct) geometry of the molecule.