When you're in parts of the southeastern US, mainly Georgia or Florida, you'll see very suspect looking people along the roadside, with a big 55-gallon steel drum sat over a fire, full of brine (I think) and fresh peanuts, still in the shell and sometimes still on the tops, still with the dirt on them. You pull over, order some, and prepare to get wet and a little muddy eating them.
I think they're best eaten warm, though I've seen plenty of people eat them room temp. They're a little slimy and hard to handle at room temp, though.
You'll get wet because water gets into the shell, so when you open it (it's soft at this point, but fibrous), the water can squirt out.
The taste and texture, unsurprisingly, is very boiled potato-like, just with some peanut thrown in.
They can be simulated at home with a slow cooker or on the stovetop. The key is to get fresh (raw) peanuts in the shell, not the roasted ones you'd use for snacking. Raw peanuts, if you've never tasted them, have their own distinct flavor.
Boiled peanuts - Wikipedia
These are in my cupboard right now:
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