CodeAndReleaseVersions < Development

The foswiki.org repository and webs include:

the last stable release tgz/zip - contains the most stable / controlled version of the core and extensions (plugins, contribs, skins). Contribs are different from plugins in that they can't be disabled and typically don't add macros or extend the Foswiki syntax. External email access, LDAP and other authenticators, are Contribs (but a Contrib might also ship a plugin along with the contrib). A plugin generally fits into the Foswiki topic rendering, and adds %MACRO% statements, etc.
GIT tags - what was released in a specific version (a static tag), e.g. 1.1.9. Stable and tested.
the next most stable (i.e., slightly less stable than the release tgz) is what is in the Extensions web. Each extension has its topic, and a downloadable tgz in the Attachments section at the bottom of the page.
GIT branches - work on the next patch release, e.g. Release01x01 for the next 1.1 patch. A more controlled set of changes, but work in process - so a check out could potentially happen between related updates. Until a release is "baked" into a release tgz, and tagged in GIT, things are a bit unpredictable. 1.1.x is more predictable than master (formerly trunk) mainly because changes to 1.1.x are less drastic.
GIT master (formerly known as trunk)- this is where the development is: "in process" changes, debug code etc. No guarantees of stability; little testing.
experimental versions of extensions