As far as I know, the two main differences are in pool filter DE and horticultural DE. The latter can also be separated into horticultural AND food grade. You only want to use horticultural DE on the soil, or to control plant pests. Do not inhale DE and avoid contact with eyes and bare skin. I would wear goggles and a mask if using as a dust. Seriously.

By the way, bee people are warning about DE. When used as a dust on flowering plants, it will harm the few remaining honey bees we have left in this country.

rhizo 1
Thanks for the safety reminders. No pesticide should be used while the bees are working, I remember beekeepers made that a rule when chemical pesticides came into use. The lack of honey bees around here stands out like a sore thumb.
Silicosis from breathing silica dust in industrial applications has declined due to OSHA regulations, but no one has warned homeoners. I hope there's a warnning on the label.
Seems that dusting plants with DE isn't a great idea after all. hmm I won't use chemical sprays
Ron

What kind of pests are you fighting? I can't use chemical pestides (organophospates, etc.) so have learned quite a bit about alternative measures.

Should have been clearer, I won't use something that I wouldn't want children around. I feel a lecture coming on from someone who obviously knows more than me.
My question was ; does anyone know the difference between what is used in pool filters and horticultural DE. The real difference not the industrys drivel.

No lecture was coming from me, if that's what you're hinting at. I was just suggesting that because I can't use the standard chemical pesticides, I happen to have some good tricks up my sleeve. That's why I wanted to know what critters you're worried about.

Attached is a link that explains the differences in diatomaceous earth products/grades.

Here is a link that might be useful: DE information in a non-lecture format

OK, I had that one coming. I read the second part of your post as a question, I see that it's a statement. I aplogize for that.
Great link, just what I needed to know.
I'm growing gourds and black beans this yaer. I just bought this neglected house and property, and need to do a lot of work before diong any more planting.
Lots of white grubs, cut worms, squash bugs will be here soon as well as mexican bean beetles.
I've orderd nenatodes for the chafer grubs, cutworms, and fire ants. After reading the artical I think I'll use DE for the bean beetles. Still not sure about the squashbugs yet.
Every thing is going on trellises so vine bores should be got with the nematodes.

Geez-Louise! Between reading a previous lengthy post on ticks and Lyme Disease, and now reading about the DE I've been using (in my attempts to organically subdue an overgrown property's bugs-of-all-kind population), I am pretty freaked out! Would like to hear some stories of gardeners who have overcome the hideous pests. . .without getting Lyme Disease or lung diseases in the process.