Lye is one of the main ingredients in soap making. Pioneers made their lye from scratch, by saving wood ashes from their fires, then trickling rainwater slowly through them, into a barrel. They'd save rendered clarified fats for their soap recipes, collected from the slaughter of chickens, pigs and beef etc. They'd make enough soap for the entire year on their annual soap-making day. Soap making can be fun and easy, but first, a few words about safety.
Ventilation is important whilst soap making, as is avoidance of breathing lye fumes.
Try to wear rubber gloves and eye protection of some kind, as lye burns and is a skin irritant. If lye accidentally comes into contact with your skin, wash the area well with vinegar, then flush with plenty of fresh running water. If splashed into your eyes, flush well with water and consult a physician immediately. Lye doesn't remain lye during soap making. Use plastic or wooden spoons for stirring.