Most people use the word ceramic to refer to anything made of a nonmetallic mineral, such as clay, and permanently hardened by heat, though it can describe the manufacturing of those items as well (e.g. earthenware, porcelain, or brick).
Ceramic materials are brittle, hard and strong in compression (forces pushing or pressing on it) but weak in shearing (forces moving parallel to the surface, such as wind) and tension (forces pulling on it). They withstand chemical erosion that occurs in other materials subjected to acidic or caustic environments and can generally can withstand very high temperatures, up to 3,000°F (1,600°C).
Most ceramics are crystalline and good thermal and electrical insulators but poor conductors of electricity. Glass is not a ceramic because it is a non-crystalline matter, but there is overlap in the manufacturing processes and the mechanical properties of glass is similar to ceramic materials.
A glass-ceramic is made when cast or molded glass becomes partly crystalline during additional heat treatments after the initial fabrication. Glass-ceramic is most widely known for its use in cook-tops but also serves as a glass composite material for nuclear waste disposal.