Laissez Faire in economics means policy of the government to let take economy and trade its own course and interfere as less as possible. In other words, it means a free market economy.
The term Laissez Faire is a French phrase which means "leave it to be". It is believed that the doctrine of laissez faire was first spread by Jean-Baptiste Colbert, the finance minister in King Louis XIV's government.
Popular economist Adam Smith from Great Britain was strongly in favor of the laissez faire policy and it was further popularized under his influence.
The Laissez faire model of economics hasn't garnered strong support after since the onset of 19th century. In fact the Great Depression of 1930s was believed to be caused by laissez-faire capitalism policy followed by many countries at that time.