Picture of Tonsil Stones
Tonsil stones (also called tonsilloliths) form when bacteria and mucus get trapped and calcify in your tonsils' nooks and crannies, leaving a hard piece of matter and a bad taste in your throat. Although those bad smelling lumps can be uncomfortable, they usually are harmless.
Image Source: Greg Ceo / Stone+ / Getty Images, (inset: Dr P. Marazzi / Photo Researchers, Inc.
Text: "Tonsil Stones: Treatment and Prevention", WebMD Medical Reference