Subsurface scattering (SSS) is used to simulate light which enters the material, scatters inside, and then comes back out (like wax, skin, food).
This scattered translucency can be colored by a texture and a color wheel.
You can set the Radius scale (maximum light path lenght), and a strenght slider.
If using Eevee enable the translucency button.
Ambient Occlusion slider set the amount of the effect if an AO texture is present.
Metallic slider defines wheter the material is Dielectric (Black pixels on the texture) or Metallic (white pixels).
Specular slider sets the intensity of specular reflections. Sp Tint allows coloured reflections.
Roughness value controls the radius of reflections blurriness: 0.0 (black) means sharp reflections (mirror-like), 1.0 (white) means totally diffused bounces.
Roughness is one of the main controls that impact on how a material looks.