Why do dogs rub their s on the carpet? It's like a scooting motion. What's that all about?

usually its plugged glands, could be worms but most likely glands. take it to vet where they will "express" them, clean them out and they are fine. Main cause of plugged glands is the poop is hot hard enough to clean out the glands when they go potty. But still happens sometimes anyway. Check with your vet ASAP