A tincture is a concentrated herbal extract.  The extract is made by soaking the herbs, roots and berries in purified water and alcohol (ethanol).  The combination pulls out the active ingredients in the herb, concentrating them as a liquid. An herb, once tinctured, will retain its medicinal properties longer than in most other preparations. 

Tinctures have been around for millennia and are a key component of traditional herbal medicine.