Upstream/Downstream

Definitions

In open source, upstream is the original project you forked from or depend on; downstream is projects that depend on yours. Contributing 'upstream' means sending fixes back to the original project instead of maintaining local patches. In data pipelines, upstream produces data and downstream consumes it. The direction of dependency flow.
In plain English: Upstream is where your code comes from (the original project); downstream is everything that depends on it.
Example: "Don't maintain a local fork — contribute the fix upstream so all downstream users benefit and you don't have to merge every release."