Air-conditioner is a kind of machine used at home, at the office or in the shopping hall and any other places. It is designed to change the air temperature and humidity within an area. Air-conditioner is used for cooling and sometimes heating depending on the air properties at a given time to create more favourable conditions. It's frequently used during in the hot summer. In the north of China, it's used for heating in the cold winter. I like air-conditioner in the summer days and nights. Once it turns on, the cool air will spread all over the room and I don't want to leave there anymore. But people often feel dry in the air-conditioning area. Therefore, remember to drink more water to prevent you from too dry.