Small pieces of code that run in the cloud on demand — you pay per run, and there's no computer of yours switched on in between. "Edge" means it runs geographically near the user, for speed.
Why it matters: the standard cheap home for agent plumbing — webhook receivers, scheduled jobs, small APIs. Occasional workloads cost pennies; you'll hear these terms in every architecture conversation.
More in “Keeping it running in the real world”