Exposition is. The funny thing is, JMS swings it far better in Centauri scenes. I mean, Midnight on the Firing Line has Londo give Sinclair the all important information about his death dream and it doesn't feel forced, and in Born to the Purple, Londo and Adira convey information about a society they both come from which still doesn't feel redundant (presumably because when Adira says "I am Centauri; your title pleases me", it comes across as half-teasing, half serious and conveys something about the relatioship as well.

...and then we have Lorien in season 4. Who could be called Walking Exposition. *cringes*