What makes hot air balloon to float ?

I have seen in the t.v. balloons floating in the air. Even people use hot air balloons to travel. Question came up in my mind why hot air balloon floats? Normal balloons according to my knowledge will not float . ????? ???????? ?????? It is because of change in density of air . As air becomes hot , its density becomes less meaning it becomes lighter than the surrounding air . As now it has become lighter , it floats . Same thing is used in hot air balloons . Now to land down , they make the hot air to get ventilated. Now density of air is becoming more and balloon will descend .