It sometimes lists rank within a particular organization. EG: Tower of Despair's final raidboss - Horoth's title is "First General of Shavarath", as he is the highest ranking general in the devil army. Or others simply specific's which house a particular npc may belong to.
Keep in mind these can be toggled on and off in the UI settings. So turn yours on if your interested in seeing these.
Currently players may not have titles, but this has been hinted as something that may be added in the future.