Herbal medicine can be administered in various forms including as a tea, capsule or tincture. Tinctures are a method of extracting the plant’s active constituents using ethanol. The herb is macerated in the alcohol, often vodka, for 6-8 weeks and then pressed through a filter and the marc (solid plant matter) is discarded. The remaining liquid or tincture contains the active constituents from the plant.
Whilst a tea will extract water soluble constituents, ethanol will extract other non water soluble constituents. This can be beneficial depending on the action you want the herb to have. For instance if you have a sore throat you might want more of the resins and essential oils from the plant (Sage for instance) to fight infection and reduce inflammation in which case you could be better off taking a tincture. Meanwhile if you have a digestive complaint you might go for a tea, (Marshmallow perhaps), as water is more effective at drawing out the mucilaginous, soothing properties which would be more appropriate for this condition. This is a bit of a generalisation but it’s just to give you an idea of how a preparation might be used.
Other advantages of tinctures over teas or capsules is that the herbal extract is generally more concentrated and the preservation properties of ethanol means the tincture will degrade less quickly. Tinctures are easy to take and as some herbs do not taste terribly pleasant they can be more palatable taken this way. Only small amounts are administered medicinally so the alcohol intake is minimal. Obviously tinctures are not appropriate for everyone including children and those don’t want to take alcohol for health or religious reasons, in which case effective alternatives are substituted.