Liquid Malt Extract (often called LME) is a condensed form of Wort that only contains about 20% of the water from the original wort. Wort is created by using heat and water to remove the sugars in malted barley and it is the base for brewing beer. Once LME is added to hot water it becomes Wort again and can be used to brew beer. Using Liquid Malt Extract can greatly reduce the time it takes to brew beer because you can cut out the steps of mashing and sparging. A substitute for LME is DME or Dry Malt Extract.