One of my favorite herbs!
Soapwort contains a chemical constituent called saponin which will lather like soap when you add water to a handful of flowers and rub your hands together. Try it with kids as a fun way to wash up after working in the garden. Historically, it was used for washing hands and fabric, and it's other common name, bouncing Bet, refers to it's use by a washer-woman or "Betty". I have also seen an 18th century painting with soapwort growing and floating in a basin by the door of a privy for hand washing. Are you are among the people who don't like cilantro because you think it tastes soapy? That's because it shares the same chemical which enables soapwort to lather!
It can spread quickly, so I prefer planting it along fences or walls where it can run free for the bees and hummingbirds that enjoy it.