Years ago, stainless steel cookware was shunned by professional chefs because of its lack of uniform heat conductivity. Some manufacturers offered stainless sets with a token copper cladding on the bottom. The consumer assumed the copper improved conductivity, but its thickness was insufficient to make that possible. Buying top shelf cookware is not a matter of mimicking the pros. You save money when you do it right the first time.
Stainless steel is an alloy which contains iron and other metals.
This is acceptable for utensils but not for cookware. A gauge of 1.5mm is a good standard in a copper or aluminum sandwich construction. A higher gauge makes for better conduction but it also makes for a heavier pot. It's a matter of what your biceps can handle. Beware of cookware that boasts many layers but little in the way of thickness.