A 'shadow' is when the sun (or a bright light) makes the outline of a person or object behind them. You can also say that someone or something is "in the shadows" if they're in a dark area where you can't see them well.
This blog is mainly to explain a different English language expression every day. Sometimes I post other stuff. I also have a YouTube channel which is mostly about computer software: https://www.youtube.com/englishspacedog
