This is the original game. Settlers of Kalguur is the newest league (think “season”) launching at the end of this week.
PoE 2 goes into early access sometime later this year, whenever that is. Regardless, they’ll be two distinct experiences, with many players planning to devote some time to both.
If you’re interested in starting PoE, my general advice is that the best time was yesterday. In this case, with a new league starting this week, I’d still encourage anyone to play around in the non-league standard just to get an early feel for things before Friday. PoE has a notoriously steep learning curve, so it’s never too early to log a few hours and experience the opening acts.