Clarified butter is melted butter with the water and milk solids removed. It’s made by heating solid butter until melted and boiling point is reached. At this point the water in butter evaporates and the milk solids float on top and also sediment at the bottom of the pan. The heated liquid butter is cooled and then passed over a muslin cloth to remove all the solids. This leaves behind pure liquid butter fat which is the clarified butter. It’s always good to use unsalted butter for this process.
Removing the milk solids increases the smoke point of the clarified butter so it can be used to cook at higher temperatures and it also increases its shelf life.
What is the advantage of clarifying butter?
Clarified butter has a higher smoke point (485°F/252°C) than regular butter (325–375°F/163–190°C). It’s better for cooking because it will not burn easily. (WIKI)
Clarified butter also has a much longer shelf life than fresh butter, because all the milk solids have been removed. It also has a nice taste.