What are they?
And how do you get/ breed them?

They are pre-revamp pet, you can look for them in the advenced shearch if you turn all the trait at none. You can't breed regenerable pet, their ofspring will not get any regen points.

do you look for a perticuliar speacie ?

Regen pets are pets who were affected by one of the Species Revamps done by the admins.

Since the site has grown so much from the time it began, the admins decided that they wanted to update the looks of some of the older pet species - they have already revamped the Qitari, Vulnyx, Zolnixi, Sylvorpa, Aurleon, Morkko, Kelpari, and just recently, the Ny'vene.

Some of the revamps involved moving traits to different slots, so the pets with those traits would look very different from their original appearance. Those pets are often eligible for regeneration- that is, their traits were turned into "trait points," and their owners could redesign them with the traits (and sometimes colors) they wanted.

The only way to get older regens is to buy them.
But keep an eye out for revamps coming up - if traits get moved, it's possible they might be eligible for regeneration!