A healthy soil is one that is easy for roots to grow, loose, and has a rich agglomerated structure; where water, air, and nutrients necessary for root growth are met.
In general: a healthy soil must have 3 major good properties: 1, physical, 2, biological, and 3, chemical.
Specifically, a good soil physical structure ensures good drainage, air permeability, water retention and fertility, and creates a good environment for microbial reproduction and growth.
The rich and diverse soil fauna constantly decompose organic matter and mineral particles in the soil, thus providing quick-acting nutrients such as small-molecule organic matter, phosphorus, potassium, calcium, magnesium, etc. that can be used for plant growth in interaction with plants.
This is where the soil comes to life! A healthy soil is formed by a combination of humus-rich, good organic matter and diverse microorganisms.