It's when you the the poo out, but leave the wet so it forms a base. Some people will leave the wet for ages, some take it out at weekends.
Can be for various reasons - saves time, creates heat, stops the base being kicked up, etc.
Like mollymurphy said - you take out the droppings and excessive wet then tidy the bed and the banks, then every so often you take the whole bed out and wash the floor etc then relay the bed. Some people swear by this method, but personally I hate it - it's only labour saving in the short term!! It've very good for older horses though, that need their joints kept warm etc.
Mine is deep littered and I swear by it. i will only remove wet when it comes to the surface of my "base" and throw up the top o the bed every other day to keep it clean and poo free!! I also turn the banks every other day, and do a thorough skip out inbetween. It only works if you keep the bed deep enough, but I love it, and my horse who can be a bit of a box walker stays dry and clean with this method
who rates shavings over straw also? at my yard there is a mix between the both, as straw is free, although makes me think if you layed on it, it wouldnt be very comfy! but neither would shavings!
I deep litter both my boys on shavings as one eats straw and the other trashes straw beds works well for both of them, straw is free for us shame but they prefer the deep litter
I do what KatB does, and it works brilliantly. Axey always seems to go through to the floor no matter how deep his bed is, and with this method he doesn't. And it doesn't take me ages to muck out either
I use shavings and deep litter beds though I'm experimenting with Hemcore. Veteran has half stable rubber mats, mucky mare (hence Hemcore experiment) not. On a freezing cold winters day, with the rain lashing down and the wind screaming, I can muck out and do beds, water, haynets, feeds, squelchy trip (cursing all the while) to the muck heap for 2 horses in 45 minutes. Is this a record???