Question about various sugar builds

[Seong-June Kim]

Hello,

Could someone teach me the difference between the images maintained at

http://olpc.download.redhat.com/olpc/streams/development/

and what is called "joyride", and sugar-jhbuild?
And are there any other branches one should follow as an activity 
and/or  core developer?

Please also let me know if this question should be directed elsewhere or 
if there's already an website with such information.
Thank you.

-Seong