The sp3 orbitals are formed from 1 s and 3 p orbitals. The energies of the there four orbitals are generally averaged forming four equal orbitals. These orbitals are spread out uniformly in space forming a tetrahedral geometry. The tetrahedral shape allows the easy formation of direct sharing and overlap of electron density for sigma bonds and double pi bonds.
sp3 orbitals allows elements like carbon to spread the valance electrons out over 4 equal orbitals to increase bonding. Carbon that has hybridized forms 4 bonds. Carbon that has not hybridized can only form 2 bonds as in Carbon monoxide. This is because there are two paired electrons in the 2s orbital. Paired electrons do not easily form bonds.
