Herbs can be preserved in a variety of ways for use at a later date, thus allowing you to use herbs that may not be freshly available. How the medicinal properties of herbs are extracted and preserved are dependent on the solvent (liquid) used, and what purpose that the herb will be used for. For examples, alcohols can extract resins from plants, and water is used for mucilages.
Tonics are herbal preparations intended to be used regularly over a long period of time, to support the body to stay in balance. Tonic herbs support our overall well-being, and usually have a particular affinity for specific body systems such as the immune, detox, cardiovascular and nervous systems. "Tonics" can be made with a variety of liquids, including water, vinegar, and alcohols.