Testing Addons in Prefs on 2.8

Newbie question, i see loads of addons in the testing column of the prefs panel in 2.8. What are these and why do most of them say 2.8 upgrade required.

Most of the addons are from 2.7x and earlier, and some need to be upgraded by the addon creators to work with 2.8. Sometimes this is simply an edit in the addon that changes the versioning to 2.8, in other cases it requires a slight rewrite in sections of the python code to use the current version of python that Blender is using or to bring it in compliance with current APIs. Sometimes this can and will be done by the addon developers and sometimes by the community if one is good at python. In many cases, everyone was waiting for feature/API freeze before getting into anything. Now that the RC1 has dropped and RC2 drops soon, addon developers can start making changes, some already have before the release candidates.

Thanks very much for that explanation.