A Life universe is a fictional Universe, where everything lives, either in a fairy-tale way, or via the laws of said Universe being so complex, that all non-organic matter becomes organic.
The Life universe is only a thought experiment, but since its the opposite of the Death universe, which has no life, it has a few variants as to what "everything is living" means.
The first kind of Life universe, is one that can and does, actually exist. The laws of such verses are complex, varied and expansive enough, as to allow life formation at any and all scales, from most any materials. These verses are unbelievably rare, but most known are naturally made and not artificial, as they are sometimes too difficult to even construct.
The second type is a fairy tale version of the Life universe, a fiction which has existed throughout our (mankind's) history, and that is a variant, where everything that can be labeled and is large enough to be seen with the naked eye, is alive. Things like water, rocks, tools, fingers, mountains, clouds, etc.
A third and much more absolute and literal version of the Life universe, is one where literally everything is alive. The particles, time, space, the Universe itself too.
A fourth but much less popular version, is one where every single subset of a Universe is living. This theoretically would include as many living beings as possible, and can be called an excessive life universe.
When a Life universe collides with a Death universe, they together create a "normal universe". This definition is purposefully arbitrary as to what it means. This usually means a Universe with some average lifeforms that may grow advanced one day, but that would create an inbalance between the Life and Deaht universes, with a dowside for the Death universe.