Hybrid orbitals are orbitals of equal energy produced by the combination of two or more orbitals on the same atom. The number of hybrid orbitals produced equals the number of orbitals that have combined.
One 's' and two 'p' orbitals when mixed together they form tree 'sp2' hybridized orbitals, if 3rd 'p' orbital also have an electron then it forms a pi-bond.