By transferring or sharing electrons, a bond is formed between the atoms. The covalent bond plays a vital role in the formation of many organic molecules. A covalent bond is formed with the sharing of electrons between two atoms; it is mainly σ-bond and π- bond.
A sigma bond is formed with end-to-end overlap of orbitals.
A π bond is formed with a partial or a side-wise overlap of orbitals.
Hybridisation is defined as the “hypothetical intermixing of nearly the same energy [of] atomic orbitals to give [an] entirely new identical equal energy orbitals”.
It is also defined as,
“Combining of atomic orbitals have different energies or ...