Explain what is meant by sp3 hybridization

sp³ hydbridization is the formation of 4 equal hybrid orbtials (same characteristcs) by the hybridization ("mixture") of two different kind of orbitals: 1 type s orbtial and 3 type p orbitals.

Explanation:

This hybridization is the result of the rearragement of the valence electrons that originally are in s and p orbitals, forming the new hybrid  orbitals (sp³).

This is easily explained with carbon atom.

Carbon has atomic number 6, hence it has 6 electrons.Thus, the electron configuration of carbon is: 1 s² 2s² 2p².So, there are four valence electrons that are in the 2s and 2p orbitals.The hybridization consists in that the four valence electons, instead of remain in two different energy levels (s and p) will form 4 orbitals, named sp³, each with the same energy.In summary the four electrons originally distributed as 2s² 2p² will be located as 2 sp³.