Lets look at 2 cases:
i) When the neutral body is a conductor:
If a charged body is brought near a neutral body, the same charge in the neutral body would get repelled and go to the far side hence accumulating the opposite charge in the near side. By coulombs inverse square law the attraction force on the nearer side overweighs the force of repulsion from the farther side . Therefore a neutral body Is attracted by a charged body.
2)When the body is a dielectric:
Since in dielectrics the electrons are bound to the atom, the atoms get polarized in the influence of electric field created by the charged body. Therefore in the same way As case 1 it gets attracted to the charged body.
Well, ofcourse the attraction is because of electrostatic forces of attraction.
Coming to the next part of the question; the neutron and proton are point charges so there is no question of charges getting polarized so there is negligible force of Electrostatic attraction. Since the protons and neutrons are in the nucleus, nuclear forces operate (at very close distance nuclear forces are immensely strong). The electrons being in the orbits around the nucleus, the nuclear forces are very weak.