Upstream

“Upstream” means the original version of a piece of software, as opposed to a copy or variation of it made by someone else. More precisely: the project that another project is forked from, or a library or dependency that it is built on. The upstream project is maintained by the original authors.

The term usually comes up when discussing versions, bugs, or patches. For example, a bug that originates in a dependency is an “upstream bug”, and a fix submitted back to the original project is “sent upstream”. When this site says “use the upstream distro” or “refer to upstream documentation”, it means to use the original project or its official documentation rather than a derivative.