Sand is the largest particle in the soil. When you rub it, it feels rough. This is because it has sharp edges. Sand doesn't hold many nutrients or water. Silt is a soil particle whose size is between sand and clay.
Silt feels smooth and powdery.
When wet it feels smooth but not sticky. Clay is the smallest soil particle. Clay is smooth when dry and sticky, or plastic when wet. Soils high in clay content are called heavy soils. Clay can hold a lot of nutrients, and some kinds can hold quite a bit of water, but the structure of clay doesn't let air and water move through it well.