In art, the term medium (plural: media) refers to the material used to create an artwork. This includes substances such as oil paint, watercolour, acrylic paint, charcoal, graphite, pastels, ink, clay, bronze, marble, and digital tools. The medium determines the physical properties of the finished work - its texture, sheen, permanence, and the techniques available to the artist.
A type of balance is a principle of design (symmetrical, asymmetrical, or radial balance), not a term for materials. A spiritual guide has no standard meaning in art terminology. The mood of a painting refers to the emotional atmosphere conveyed by the work, which is influenced by the medium but is not what the term "medium" means.
When describing an artwork, identifying the medium tells the viewer what the artist physically worked with. For example, "oil on canvas" specifies both the paint type (oil) and the support surface (canvas) as the media used.