The rear tires of many tractors are loaded or filled with liquid or foam to give them more weight. The greater the weight the better traction and stability in most cases. The liquids can be water, windshield wiper fluid, rim guard and so on.
No question is stupid if you really don't know that answer.
Loaded tires are liquid filled (75% fill) usually only rear tires on a tractor. The liquid can be one of several things with plus and minus points to all of them. Common things are: Water, Calcium Cloride mix, Windshield washer fluid (water and Methanol). RV anti-freeze (Propylene glycol.. non toxic) Regular anti freeze mix (toxic Ethylene Glycol water mix) Rim-Guard (beet pulp/juice byproduct) and others. What do they do? They add needed weight to the rear of the tractor and also lower it's center of gravity. Why would you want them? If you operate a Front End Loader (FEL) you need more weight than the tractor comes with. You also need weight on the 3pth hitch, but it can help to have the loaded tires also. Another reason is you operate on slopes, the lower center of gravity can help stability. Like everything else there are upsides to loaded tires and downsides to loaded tires.. you can read here for hours.. Let us know if you need more..
Actually it's tires that have had too much to drink.:laughing::laughing::laughing: sorry I couldn't resist Again no question is dumb if you don't know. I've been around tractors a day or two and just figured out what was meant by FEL.