Photon scattering is not clear to me. [I trust this is not a tangent to the thread.]

Just what is going on when a photon encounters a particle much smaller than itself. In elastic scattering (Rayleigh), the wave length is unaltered but its direction, and polarization, I think, are changed. Is it...
1) an electromagnetic reaction to the electron shell(s)?
2) a diffraction issue?
3) a particle bounce?
4) an absorption and re-emission?

I am guessing an inelastic scatter (e.g. Mie) is no. 4, right?

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