Gold leaf is real gold that is beaten into extremely thin sheets. The thin gold sheets are commonly used for gilding. Gold leaf is available in a wide variety of karats and shades. 22 karat yellow gold is the most commonly used.
Gold leaf is often confused with Metal leaf but they are completely different products. Metal leaf is imitation gold that does not contain any real gold. Real gold leaf is almost pure gold.
Traditional water gilding is the most highly regarded form of gold leafing. It has remained virtually unchanged for hundreds of years. Modern machinery can not do what an experienced gilder does by hand.