I've skimmed through Wikipedia's article, as well as as PSE question What is a phonon?, but I am still entirely left in confusion as to the types of phonons and their corresponding characteristics and differences.
From what I could gather, there are:
Acoustic phonons. These are vibration modes of the crystal lattice and are coherent (they move in phase). They can be in the direction of propagation or not. I think these phonons are created when we either displace the whole crystal, or deform it mechanically. In a way, they are the "sound waves" in the crystal/material.
Optical phonons. These are out-of-phase vibration modes of the crystal lattice, meaning neighbor atoms or ions are moving in opposite direction. These phonons are usually activated (or created) when light (usually infrared but not strictly) is shone on the crystal. These phonons are responsible for the Raman scattering.
Thermal phonons. Unfortunately I am unable to retrieve much information on them, but I suspect they are the two kinds of phonons described above, so maybe this section is not valid.
Virtual phonons. From what I could dig on the Internet, they are responsible for superconductivity. In this case, Cooper pairs are deforming (I am not sure whether the deformation is real or not) the crystal lattice, creating these phonons. Unlike the optical and acoustic phonons, these phonons would still exist at absolute zero temperature. In Wikipedia it is written that "At absolute zero temperature, a crystal lattice lies in its ground state, and contains no phonons." This is why I assume that the virtual phonons are not real deformations of the lattice. But then, what are they?
I would greatly appreciate if someone could correct any mistake I wrote above, and shed some light on all the currently known different type of phonons and their corresponding characteristics.