I've purchaed a plumeria Alba because it was the cheapest one on ebay, it was still beautiful, like a common celedine. I didn't notice much difference, though? (is there any at all?) If yes, then what is it? the number of flowers per stem?
Thank you.

Plumeria alba is a different species from Plumeria rubra. The leaves are very different and the flowers will always be white. Plumeria rubra is the only one that can have colored flowers.
Check the database for Plumeria alba pictures
Plumeria (Plumeria alba)

Well, this is odd. The seller sold me, supposedly a alba cutting and I thought that it looks just like a plumeria rubra in the pictures(which i assume are his own) so didn't mind because they were still rubra looking... but then, is this in the pics a rubra or an alba? Help :(
Here are his pics on the item page.

the only thing to do now is wait to see the leaves...
Let's hope the seller got confused and is selling a rubra as an alba..

I've contacted the seller and he said the plumeria is the one in the pictures. As long as it is that one, i'm happy!

Yes, unfortunately many people will sell any white blooming plumeria as Plumeria alba.