Tell me the difference between bell's palsy and facial palsy?

Both facial palsies. Bell's palsy is facial weakness or paralysis that is thought to be due to a viral infection of the facial nerve. There are other causes of facial palsy including tumor growth, stroke, infection and trauma to name a few.
Sub-set. Bell's palsy is one type of facial palsy; there are many others. ("palsy" is an old term for paralysis.).

Related Questions

Can anyone tell me the difference between bell's palsy and facial palsy or they are the same?

Not exactly. While both present with inability to move one side of the face, bell's palsy is a diagnosis of exclusion. Other causes of unilateral facial paralysis (lyme disease, stroke, ear infection, ear or brain tumor, etc) need to be ruled out during the evaluation. In short, all bell's is facial palsy but not all facial palsy is bell's.