الْوَرَقُ كَالْحَرِيرِ فِي النُّعُومَةِ.
Paper resembles silk in softness.
“Paper” is the compared subject, “silk” the model, “softness” the ground and kāf the particle. Softness can be experienced through touch, so this is a sensory comparison in an evident quality.
If one says only “Paper is like silk,” the comparison remains, but the audience needs the context to determine whether softness, sheen or another attribute is intended.