On heating appliances like cooktops in the US, they are nominally rated for 240V operation, with three wires, L1, L2, and N (neutral). A higher-end one will pull a peak power of about 10 kW with all hobs on full and the oven going on full as well, i.e. 40A draw. If you look at the label, though, you will see that many have a reduced set of specs for 208V operation. This is because many newer apartments and condos in the US use 3 phase, and sqrt(3)*120v = 208.
On a tangential note, if you apply 120V from one of the lines to the neutral, you will activate "sales demo mode" where all the features and lights turn on, but the heating elements are not activated. It increases sales, or it did when people bought these in stores. Kind of like "store mode" for AV electronics.
John