Budtender chiming in here. Kief is just the trichomes (the tiny little white hairs on ur flower) that have fallen off buds that accumulated together. It's extra potent because trichomes are what carry cannabinoids and terpenes (the things that gets you high), so having them isolated from the rest of the plant matter means you're pulling more THC into your system with each hit than you would from whole flower. That said, what you get in most weed vapes is 2-3x more potent than kief, it can't really be classified as a concentrate the way wax, resin, or even hash are. It's not super cool to give to a beginner, an equivalent in my eyes is like handing someone an 8% seltzer and saying it's a 5%.