I assume its speed doesn't change but the photons get absorbed and destructed by the materials' atoms and then they emit new photons. Is that true?
Light is an electromagnetic wave. It is an oscillation of electric and magnetic fields. The ability of these fields to oscillate depends on the medium the wave is travelling through. The least "resistance" is provided by the vacuum, so in a vacuum the speed is greatest.
In a material, the atoms (which have electric and magnetic fields themselves) influence the ability of the wave to oscillate and this has the effect of slowing the propagation.
The size of the effect (the factor by which is slowed down) is known as the refractive index of the material.