PROBLEM. I HAVE CLEANED PART OF MY CARPET, BUT WHAT SUCKS UP THE DIRT OR WATER AS CARPET WAS WET,

Question

I HAVE CLEANED PART OF MY CARPET, BUT WHAT SUCKS UP THE DIRT OR WATER AS CARPET WAS WET, I HAVE WATCHED A VIDEO, BUT DIDN'T GO FAR ENOUGH TO EXPLAIN THIS, AND WHAT DOES THE BELT DO THAT IS LOOSE FITTING IN BETWEEN EACH SIDE OF BRUSH.KINDEST REGARDS