The software world
Environment variable
env var
A setting kept outside your code that a program reads when it runs — often a secret like an API key, or a value that differs between your laptop and the real server. The code says "read the key from the environment" instead of writing it down.
Why it matters
Part of Software words you'll hear → It's how secrets and per-machine settings stay out of the code itself. You'll usually meet them as .env files.