A molecular orbital gives the electron probability distribution around a group of nuclei in a molecule such as an atomic orbital that gives the electron probability distribution around a nucleus in an atom. I didn't understand. what does it mean?
In simple words, an atomic orbital is the location where probability of finding electrons around a nucleus is maximum.
A molecular orbital is formed due to overlap of 2 atomic orbitals of the constituent atoms.
So a molecular orbital is also a location where probability of finding the electrons is maximum.