The basic utensil in cooking, for everything that needs to be cooked, boiled, heated, etc.
If you intend to buy:
Basically you need a set of good quality pans. Quality means: stainless, with a thick base, if possible with either a removable or metal handle (which can be put in the oven). Avoid non-stick pans, it's not easy to see what's going on in them, with the black bottom.