Final answer:
RAO and LAO stand for Right and Left atomic orbitals, respectively, which form part of linear combinations of atomic orbitals or LCAOs, a concept in molecular chemistry.
Step-by-step explanation:
In the terms RAO and LAO, the R and the L refer to the Right and Left atomic orbitals, respectively, which are part of the linear combinations of atomic orbitals, or LCAOs. These molecular orbitals are created from the sum and the difference of two atomic wave functions in the process of molecular bonding. By combining atomic orbitals in this way, a molecule creates as many molecular orbitals as there are atomic orbitals within it.