There are 3 groups of stainless steels: austenitic, martensitic, and ferritic. They are all known as stainless steels but they have different properties that make them suited for different applications.
The stainless steel that most consumers encounter is austenitic stainless (18-8, 18% Cr, 8% Ni) and a magnet will not stick to it. A magnet will stick to ferritic stainless which is "used extensively for kitchen equipment, dairy machinery, interior decorative work, automobile trimmings, and chemical equipment (to resist nitric acid corrosion)" (Marks' Standard Handbook for Mechanical Engineers, 8th ed., 1978).