What do "Colloidal Silver Generators" really do?

Well, most of what you'll "learn" is sales hype or repeated ignorance handed down without context...some is even partly true.
"Technically" an ion is a particle because it has mass and takes up space, but the technicality is often used to mislead.

But ions are Charged Particles, in the case of the Silver Ion,  Ag [+] and it's corresponing anion  OH [-] or Hydroxyl ion

The silverpups and ALL generators that use electricity and water make ONLY ions and  silver ions only come in one size...one atom minus an electron.

Colloidal Particles form FROM ions later, mostly in the Nernst Diffusion layer at the electrode surface/ water interface and according to environmental conditions such as concentration.

If the concentration is higher than the solubility limits of silver ions in water,the ion is forced to combine with something to make an uncharged particle.

If that particle is small enough to stay suspended in the water, it is by definition "Colloidal"

Only those ions that find an electron become "silver" particles. Electrons can be picked up at the air/electrode interface and from glass acting as a capacitor/ [very inefficient] solar cell collecting electro-magnetic radiation. There are no "free"electrons in a liquid. only electron imbalances as ions and anions.
Some of the hydroxyl anions OH[-] will combine with  silver ions to form a silver hydroxide particle or with dissolved oxygen, to form silver oxide....both, byproducts of electrolysis,
Hydroxyl rich water is also known as "alkaline water"
If the current is kept low, the oxides and most of the hydroxides form and stay on the electrodes where the SWAP current reversal phase re-converts most of it back to ionic silver.
The more particles in a given volume, the higher the odds of them growing bigger and they don't come in one size, but ranges of sizes with the vast majority of the silver still as ions.
Current control controls current density on the electrodes and keeps that concentration down in the diffusion layer so fewer and smaller particles tend to form, but the water itself plays a role too and water is highly variable.

No generator that uses electricity and water makes "particles" AT ALL.

They make ions and nothing BUT ions and silver ions only come in one size or they aren't silver.  No "particle" of silver can possibly be smaller.
A silver ion, by definition: A single atom minus an electron at 0.000252 microns diameter

0.000252 microns = 0.252 nanometers

If anyone answers the question " What size are the particles this machine makes? " with a number, they are either liars or suffer from ignorance.
With 85% to 97% of the silver being ionic, smaller than a single atom by definition and nothing smaller possible, does it really matter?
Particles bigger than around a couple of microns settle out and are, by definition, not "colloidal".
Leave those on the bottom.

The formation of particles *out of ions* happens within the environment which includes many variables.

The variables that the SilverPuppy machines CAN control are controlled, but there are many that a generator can't control.

Further, particles form in size ranges with a distribution of many sizes, so one figure just isn't going to describe anything *real*.

Exerpt from "Colloidal Sciences Laboratory" [Frank Key]  http://www.silver-colloids.com/Pubs/TEM.html

[I]n order for the TEM to photograph particles, all water in the solution must be evaporated. When that happens, any silver ions in the solution form a silver oxide compound. Because the number of silver oxide particles is far greater than the number of silver colloid particles, it is the particles of silver oxide which predominate in TEM images. So, what is represented as images of colloidal silver particles are really silver oxide particles . . . and they are not the same thing at all.  Further, the particles depicted in the TEM images do not represent particles in the actual solution, but are actually created in the process of removing the water for the TEM imagery, further invalidating the image.

[ie:  The particles depicted in the photo were never in the water being tested, therefore the whole concept is totally bogus, uttery useless as "proof" of anything ]