Hybridization means the mixing of atomic orbitals to yield hybrid orbitals with characteristics that are different from that of the isolated atomic orbitals before the combination.
sp3 hybridization occurs when one s orbital is mixed with three p orbitals to yield four sp3 hybrid orbitals which can be used to bond to a central atom.
The central atom is then located at the center of a regular tetrahedron at a bond angle of 109°.
