I wish to know about Jills. How do they differ from normal dragons and what do they have in common with them based on the lore we have now? All I really know is that they are basically the dragon's versions of angels (whatever that means), they appear during Dragon Breaks to mend time, and are always female.

All dragons are the dragon god's angels, if you were to say such a comparison. It's just that Jills are time menders, and do 'service' the time god.

Old lore and it's uncertain how they fit in now that Skyrim has come.