Soft polytheism is the belief that there are many Gods who are all part of a larger whole.
The whole may be a Divine source or Godhead that has many aspects and each of these is recognized by the mortal mind as a God. In many cases, the Godhead does not interact directly and the only way to interact is through its representative faces. This may or may not include a pantheist or panentheist model, in which everything is part of the Godhead, which would naturally include all spirit beings.
Another definition of soft polytheism used in modern language identifies the whole as the human subconscious on an individual or collective level with each God representing an archetype or aspect of the human experience of the natural world in a symbolic or archetypical way. While this may seem an atheist approach, it is often a part of a pantheistic or panentheistic worldview. The idea is, there is but one Godhead, huge and unknowable in/of everything, and we connect to it through archetypes which are really part of us, while we are in turn each part of the Godhead.
In everyday interaction, many soft polytheists relate to Gods on an individual basis in a way that would be just as appropriate as if they were unique individuals and interaction with the larger Godhead is featured as part of deeper mysteries.
Contrast hard polytheism