Potions work much like any other magical practice. They allow you to use the energies of different ingredients, objects, and tools to cast a spell. Mixing and/or using a potion with a specific intention in mind will increase the power of your magic.
The herbs, base liquids, crystals, and other ingredients used in potions each hold their own energies and properties. For the animist witch, these ingredients even have a spirit and consciousness of their own. In working with these spirits and energies, you can build a desired intention or effect through combinations and then upon using these potions, those energies will draw your intention to you. This is true even of spells for banishing or binding! For those who are interested in making potion crafting a heavy part of your practice, building a relationship with the energies and spirits of the ingredients you use can greatly enhance your magic.
The key idea behind potion-making is that the liquid will hold the energy of whatever ingredients were used in the potion-making process, even if the magical objects or herbs were strained out. This makes transforming, combining, and preserving those energies very easy.