Stainless steel is an alloy made of iron, chromium, and other elements that gives it excellent corrosion resistance. There are five main types - ferritic, austenitic, martensitic, duplex, and precipitation hardening - with varying compositions and properties like strength and magnetic response. Stainless steel is manufactured through processes like melting, casting, hot and cold rolling, annealing, pickling or electropolishing to remove scale, and various forming and finishing steps before being used in a wide range of applications.