Sometimes you paste a URL and it looks like gibberish - lots of %20 and & symbols. That's URL encoding, and it's actually pretty clever.
URLs can only contain certain characters. Everything else needs to be "encoded" into a format the browser understands. For example, a space becomes %20, an ampersand becomes %26.
When You Need a Decoder
If you're debugging API issues or trying to read a messy URL, a URL decoder is your friend. Paste in that encoded mess and see exactly what it's trying to say. Super helpful for developers!