ECT stands for electronically controlled transmission, this mode of transmission is used to haul something like trailer, or it can be used in hilly or mountainous areas too. this button should be pressed only when your vehicle is under stress or heavy loaded. but remember it costs more fuel.
2nd: as it indicates that the vehicle is on 2nd gear only. it is used in slippery road like ice, where keeping the vehicle on 1st gear keeps the tire spinning.