Type 0, bare bones casting.
In which magic is done by raising, shaping and releasing energy through a combination of visualization, meditation, chants and incantation and ritual movements. Typically, if any outside materials are used, its solely to facilitate this process, such as recorded drum music, cushions to sit on, and so forth.
– when materials are called for, typically this is to give the energy a physical form that can hold it over the long term, let the witch shape the energy more easily, give the energy a toe hold in the physical plain, and generally make it easier to work with.
Type 1, Materia as sympathetic Magnet.
A symbol of a thing holds a spiritual connection to the thing it resembles. By assembling various kinds of symbolism into an item, the witch can turn that item into a physical link to the forces she wishes to attract, or repel. Much like how a magnet will tract iron, the item will attract the concepts to which it is sympathetically linked.
Type 2: materia as energy container.
In this model, the items used in the casting proce3ss act as containers and shapers of the energy the witch provides. Much like how a glass holds water, and the water contained within the glass takes on the shape of the glass, the energy flowed into the item by the witch takes on the sympathetic qualities of the item. The item can also hold, and radiate the energy on the long term, freeing the which up to go about other tasks while the energy goes about its work. This is very useful for witches as the ability of the materia to shape the energy into its desired concept lessens the burden on the witch. She doesn’t have to visualize as intensly as the items do some of the programming for her.
Type 3: materia as targeting aid.
By taking a some form of material from your intended target, then surrounding it with symbols (physical and non physical) of your desired effect, the material component in this case acts as a stand-in for your desired target. Allowing castings to be performed when the target isn’t present and over long distances.
Type 4: materia for inherent properties.
Many materials used in magic are values not for a symbolic or spiritual property, but for they’re literal, physical qualities. Many stones, crystals and herbs fall under this quality. As they’re chemical makeup makes them useful as remedies for various ailments. A good example is white willow bark being useful for its pain lessen abilities. Or witch-hazel as an astringent.
Note: not all spell components are physical. Verbal and meditative techniques can fit the profile for type 1 and 2 easily.