That's the common vernacular, but I call them RWC- Red Worm Castings.
The castings we growers typically use are produced by leaf litter type worms with the Red Wiggler being the most common. They're not soil dwellers but rather live in the top mulch layer found at the base of trees and compost piles, and such. We don't really use earthworms, at least to produce castings. They might be good in a big, deep outdoor pot to keep the soil aerated, but mostly what we're interested in is their ability to process organic waste into their famed "unicorn poop" so for that we need a different species of worm.
When organic matter and soil biology go through the gut of a worm, they come out the other end covered in a calcium carbonate slime and full of incredible microbes that can't be had easily any other way. And, depending on your inputs, the output can truly be an exceptional organic fertilizer.
@ReservoirDog has documented his extensive worm bin inputs in his journal.
And even more exciting
@Jon , once you decide to start your own worm bin, you can have all you want for the cost of the inputs which can often be had for free like kitchen scraps, yard waste, fall leaves, common yard plants like
Comfrey and Stinging Nettle, HorseTail Fern , willow, large showy flowers like peonies and day lily, and local manures from herbivores like cows, horses, rabbits and
@StoneOtter 's favorite, llama.
And, since you've decided to go organic, I'll share an
Interview with Clackamas Coot who is responsible for many of the non-traditional methods many of us use. I posted the transcript but you can listen to it online at the internet address provide at the top of the post.
In it, he talks about worm castings and the use of malted barley among other things. The guy's a bit of a legend in the organic canna world. He's working with Kis Organics and Build-a-Soil to produce amendments growers can purchase based on his innovations.
And, if you're into YouTube videos, Jeremy from Build-A-Soil has a good channel where he does weekly updates of a season's grow (several seasons now in the books) and explains the what and why's as well as answers grower questions. That's a great resource to get up to speed on all things organic.
You'll end up with your own particular style but it's a good jumping off point to give you exposure to the organic growing world.