Hardness is a measure of how much a material resists changes in shape. Hard things resist pressure. Some examples of hard materials are diamond, boron carbide, quartz, tempered steel, ice, granite, concrete. Ability of material to resist wear, tear, scratching, abrasion cutting is called hardness.
Harder materials are more difficult to cut and shape than softer ones. They are also usually more brittle which means they do not bend much but can shatter. Hard materials are used in cutting tools, machines and construction materials and other industrial goods.
Hardness tests are important in materials science. The Mohs scale of mineral hardness tests the hardness of minerals. The Brinell scale and various compression tests and rebound tests are more used for metals and artificial materials.