The frothy soap bubbles you make when you wash your hands are suds. If you put too much detergent in your dishwasher, the kitchen floor could end up covered in suds.
Besides suds made from soap (the word is actually short for soapsuds), there are other foamy, frothy substances you can call suds. Sometimes the tide leaves suds on the beach, and you may be fond of sipping suds off the top of your root beer float. Because it's often topped with suds, beer itself is informally known as suds. In the 16th century, suds meant "dregs or muck."