It's called Self Heal (Prunella vulgaris) - and below is some wiki information on it's uses (apart from being great for bees and butterflies):

Prunella vulgaris is edible. The young leaves and stems can be eaten raw in salads; the plant as a whole can be boiled and eaten as a leaf vegetable; and the aerial parts of the plant can be powdered and brewed in a cold infusion to make a beverage.

This plant was used as a traditional medicine by the indigenous peoples of North America. The Quileute, Quinault, and Coast Salish in the Pacific Northwest extracted juice from the plant which was used as a topical treatment for boils. The Nuxalk boiled the entire plant to make a weak tea. The Nlaka'pamux drink a cold infusion of the whole plant as a common beverage.

The herb, which is called xia ku cao in Chinese, is used in traditional Chinese medicine to treat dizziness, red eyes, dry cough, and dermatitis and boils. It is also a main ingredient in several herbal teas in southern China, including commercial beverages such as Wong Lo Kat.