Clay is soil with certain minerals in it. Soil with a high amount of clay takes longer to absorb water, but will hold the water longer. So, some plant do better in soil with lots of clay and others in soil with sand and better drainage. Clay can be treated with heat to make ceramics, adobe, brick and other useful home construction and furnishing materials.
Clay can be used as a fun (and messy) play toy, to make building materials, furnishings (such as dishes) or other items (such as jewelry -- beads or pendants).
Colorful, synthetic clay is also created for jewelry making and children's play.
- Wikipedia's article on clay