Plant protein powder uses proteins from various pure sources. Some of the most common sources are soybeans, peas, brown rice and marijuana, although these are not the only types available. Soybean protein isolate is a very common protein source of plant protein powder.
Many plant protein powders contain a variety of protein sources, not just one. Mixing different types of protein can give you more complete nutrition and amino acids, and can improve the texture of protein milkshake.
Unlike whey protein or collagen (derived from animal products), plant protein is not extracted from milk like whey, but from peas, soybeans or marijuana.