Human hair bundles are essentially groups of hair extensions made from real human hair. They are often used for hair weaving, which is a type of hairstyle that involves sewing or gluing the extensions onto a person's natural hair or onto a wig. The bundles come in a variety of lengths, textures, and colors to match different hair types and styles. They are typically sold in sets of 3 or 4 bundles, and the number of bundles needed for a full head weave depends on the length and volume desired. For example, if you want a fuller look with long hair, you might need 3 to 4 bundles.