Smiles!
Mycorhizae are defined in the Official Phylogynological Taxamonium as:
"A person's personal microscopic core elements of etherial nature."
The "Californians Manual of Rainbow Gardening" speaks of the useful and symbiotic probiotic relationships of organisms to co habitate with all fellow living beings in a most positive and mutually fulfilling manner, and stresses the importance of helping those organisms that are helpful to us without asking, to multiply, live, love, and enjoy their existences. The tyedyed and multifloriferous nature of these complex relations, always innately correlated in and within one's internal nature is expressed for the true gardener who nourishes planetary life as a whole as an abiding love for the soil.
Outwardly, and most coarsely mundane, and also most importantly phased as a natural course, is the gardener's nurturing of her soil. By nurturing her soil with true love and the proper manure, this multifaceted complexity manifested to our organic senses, (a means for the universe to sense and to understand its own self as an entirety), is a most beautiful web.
Naturally one must speak and discourse what it means to understand that the universe as an entirety can and does have self understanding. For this is one of the developments of the Rainbow Gardener.
>>>ha

I just thought of that stuff...stuck it in for funning!
Mycorhizae is the fancy scientific name for funguses. Funguses, they like to plural the latin way: Fungi, are more than just mushrooms and toadstools. Most kinds live in the soil invisible to the naked eye. Ever notice that real good soil has an almost mushroom kind of smell? That's all the mycorhizae in it. They make long strands of cells. What they feed on gets all processed in their cells, and then when those mycorhizae cells die, the nutrients are available for plant roots.
They help in other ways too that an expert would need to talk about.
Other microbiologicals are actual soil bacterias. They are all good, and I don't know how they do their good, but they do good.