Lines and veils are shorthand for communicating boundaries quickly. A veil is a subject someone would rather not dwell on during roleplay. A line is a subject someone does not want to encounter at all during roleplay. For this to be useful, you should talk about it when you form your roleplaying group or add new members. The lines and veils for your group should be recorded on your World Sheet. For a better explanation visit https://rpg.stackexchange.com/questions/30906/what-do-the-terms-lines-and-veils-mean