Completely new and learning

[Gemina]

Try to get into the habit of Marking targets, it's a dying art, but people will love you long time when they see it. ♥

Welcome to Eorzea!

You really only need to do this if you want the DPS to prioritize a target. Some examples would be the bees in Qarn and also the Golem's Soulstone in the same dungeon, the Voracious Maw of the first boss in the Lost City of Amdapor when he devours a player, or which ever part of the Damaged Adjudicator that glows red before it disappears in Qarn HM. However, the [1], [2], [3] markers on trash mobs in the days of old is unnecessary in most cases.