What is aquafaba? How might a vegan use this liquid?

In general one medium egg white can be replaced with 30 millilitres (2 tablespoons) of aquafaba, or one medium whole egg with 45 ml (3 tbsp).

The simplest way to obtain aquafaba is to decant the liquid from canned or boxed legumes such as white beans or chickpeas. It also can be made by boiling, steaming, pressure cooking, or microwaving pulses in water.