Small white balls in soil are known as saprophytic fungi which are not a harmful or pathogenic fungi.
The saprophytic fungi or little white fuzzy balls are just fungal hyphae and the fuzziness around the spheres are roots of the hyphae.
The little white balls in potting soil are perlite, volcanic glass heated to more than 870 degrees with an ultra-low density.
In horticulture, the purpose of perlite is to support soil drainage and improve aeration.
If the soil is just regular soil and not potting soil and you're seeing the little white balls on the ground it would be saprophytic fungi.
Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed organic matter.
It occurs in saprotrophs, and is most often associated with fungi and with soil bacteria.
Saprotrophic microscopic fungi are sometimes called saprobes.
Saprophytic fungi are the largest group of (macro) fungi, responsible for breaking down and recycling dead plant and animal material.
These are the fruit-bodies you see on dead trees, leaf litter, animal bones, even feces.
Saprophytic fungi or saprophytes can be found on or in soil and usually live on decaying vegetation, such as sticks, leaves and logs, and are commonly found throughout the environment.