I am native speaker but I haven't yet figured out the exact meaning of 追 as in 追剧 - 'chasing a TV series'. Does it mean 'stay on top', 'catch up' or simply 'actively watch'? In other words,

* Does it exclusively refer to watching the latest episode on air, or at least keep oneself up to the season?
* Does it count as 追 if I am watching the past season on DVD in order to catch up and watch the current season?
* Does it count as 追 if I am watching a series that has already finished?