Chaff is the dry, papery husks that surround grains of wheat, rice, or other cereal crops. After farmers harvest grain, they need to separate the valuable seeds from this worthless outer covering. For thousands of years, people did this by tossing the grain into the air on a windy day: the heavier seeds fell back down while the lightweight chaff blew away. This process is called winnowing.

The word also means anything worthless mixed in with something valuable. A researcher might need to sort through the chaff of irrelevant studies to find the important ones. When you're reading online, you might encounter plenty of chaff (useless or misleading information) before finding what you actually need.

The phrase separate the wheat from the chaff means distinguishing what's valuable from what's not. A teacher separating the wheat from the chaff might focus on the most important concepts instead of minor details. When you're working on a research project, part of your job is separating the wheat from the chaff: keeping the good sources and ignoring the rest.

Interestingly, military aircraft sometimes release clouds of tiny metal strips, also called chaff, to confuse enemy radar systems.