What are the differences between the dunmer and ashlander dunmer ?

Ashlanders are tribal and live out in the ashlands. Settled Dunmer live in cities.

The distinction is also cultural, religious (the settled Dunmer follow the Tribunal Temple, while the Ashlanders worship the Three Good Daedra), and linguistic (Ashlander names are Akkadian). Settled Dunmer (also called House Dunmer) are divided into five Great Houses, led by councils and ultimately by a monarch (King Helseth, at the end of the Third Era); Ashlanders are divided into five tribes (there were more, but many are now lost), each being led by a wise woman and a chief called an ashkhan, supported by honored warriors called gulakhans. Both the House Dunmer and the Ashlanders revere their ancestors, and after the reformation of the Tribunal Temple to worship the "Reclamations" (the Three Good Daedra) many House Dunmer turned to Ashlander wise women for religious counsel.

I think it was said that those were the Five tribes of Vvardenfell not that of Morrowind

Possibly. Either way, there used to be more than there are now.