Long Polling
In plain terms
A technique where the server holds a request open until data is ready.
Going deeper
Long polling keeps a client request open until the server has new data, then responds, simulating real-time updates over HTTP. It's a fallback before websockets.
Under the hood
More efficient than rapid short polling but less so than websockets/SSE; widely supported as a fallback.
Examples
Real-time fallbacks, chat (legacy), notifications, before websockets.
Think of it like...
Like asking a clerk to hold the line and only answer once they have news.