I really want to know what a turn is

[Allyrion]

Cool so how would this work in a raid in wow as an example so I better understand and how does this work with alaxander?

For example, Turn 1 is equivalent to the first boss in a WoW raid and the trash comes before that boss.
That's all there is to it.

In Alexander, it's Floors instead of Turns. Basically each Floor has trash and then a Boss.
Unlike WoW they're kept in different instances. In the old Coil, you had to move through the instances in progression though.
However, similar to WoW's LFR, you can queue for later parts once you've unlocked it in the duty finder.

So the very first time, you have to do it in order.
Afterwards, you can do basically pick any boss to fight individually.

Is there something you are actually turning in that specific encounter or is that term entirely arbitrary?

The term comes from the Binding Coil of Bahamut.
In which case, you were literally going through different parts of a giant Coil.
It was wreckage from Dalamud (the moon which turned out to be a containment machine for Bahamut).

Turn referred to the turn of the Coil, though the term was more symbolic than the actual layout.
That was the idea. You're going up a big coil, each turn of the coil had a boss inside of it.
It was the name SE decided on too, since that's what it says when you enter and what it's referred to in the duty finder.

Some people are using Turn to refer to Alexander out of habit, since Alexander is basically the new Binding Coil of Bahamut.


Also, it seems worth mentioning that Binding Coil was the raid of all of 2.0 (well hardcore raid).
Unlike WoW which has raids that are separate, sometimes unrelated (well, loosely), FFXIV had one raid story that was expanded upon.

Well, there was also the Crystal Tower which is the equivalent of Raid Finder in difficulty. So it was more casual content.
That was also technically a raid. It was a lot closer to WoW raid in design, with a lot of Bosses, and trash in between, all in the same instance.

Each was updated in alternate patches. For example, you had the Binding Coil of Bahamut (BCOB) then 3 month later you get Crystal Tower (CT) that gave catch up gear (less than the first BCOB).
Then 3 months later, you get the Second BCOB (6 months from the first BCOB) then the next Crystal Tower part in another 3 months.

That's how it basically goes in this game.
There are also Primal Bosses throughout this which are individual Boss fights that have no trash and are not connected to either of the raids.