An herbs medicine and functional effects live in its bioactive compounds. But these compounds only become available through a solvent that can dissolve them.
Each active constituent in a herb has a chemical synergy with a specific kind of liquid that it will most dissolve into. Some are most drawn (or only drawn) to water, some to alcohol, and some to fats.
This property determines which preparation (a tea, a tincture, or an infused oil) will actually capture a herb's compounds and deliver those compounds into the body.
Knowing these three solubility categories will empower you to use herbal remedies in ways where they will actually work.
As an example, the herb slippery elm bark has demulcent water soluble compounds. So this herb is best made into a tea rather than a tincture or oil extract which would not provide the demulcent action you were looking for.
In the next sections I cover the three solubility types, methods of extraction, and common compounds for each.