It’s exactly what you think it is.
Fresh Patch is a disposable plot of real, hydroponically-grown grass that shows up ready to... use. I would never advocate turning any dog into an “indoor dog”, but for aging dogs, injured dogs, dogs being house trained, or as a just in case, it’s a great product to have around.
Non-disposable dog potties have been around forever, and cleaning them (they never really get clean) is the stuff of nightmares. Your dog won’t hate themselves using the Fresh Patch, and you won’t question every decision you’ve ever made when cleaning it just involves throwing it away.