What is called Bohr’s orbits?

Bohr’s orbits are hypothetical circular paths in which electrons revolve around the nucleus. These paths have definite energy and definite radius and are sometimes called shells or stationary energy levels. The revolution of electrons around nucleus is similar to the revolution of planets around the sun in the solar system. Electrons do not lose or gain energy when it revolves in an orbit.

Note that, not all circular paths around nucleus are possible. The electrons can only revolve in circular orbits in which the angular momentum of the electron is an integral multiple of h/2π.