Go where the wind takes you.
A sailor is a person who sails. Wether it is on a pleasure boat or on a mega tanker, they are all sailors. But it is also used as a general term for all the ratings on the crew of a ship. They can be split up in three ranks OS, AB, and LS. Ordinary Seaman, Able Seaman, and Leading Seaman. Now wait, why is it AB? Because in ye olde days of hand writing AS was to simular to OS.
It is a myth that AB stands for Abled Bodied is a wrong one, but it's often repeated on the internet and therefore many people believe it.
Ordinary seaman is the staring position, and depending on a sailor's personal growth it will take one to two years to become an Able Seaman. Leading Seaman is not a rank that is much in use anymore on the world's fleet, with the ever downsizing of crews as technology advances. But on ships with large crews they are still around. They are the most experienced sailors and they help the Boatswain in leading the crew.
The rank of Leading Seaman can also be used as a bonus rank for a very experienced sailor who is a long time with the company. Simular as Commodore is used for Captains
Seaman, Sailor or Deckhand
Is it seaman or sailor? I'd say both is good, it depends on the culture within a company or on a ship, and what is the more prevailing. Deckhand is another name for a crewman who works on a ship, usually they mean a sailor who works on the deck by that. The word deckhand is a bit for a smaller group. Sailors who work in the engineroom or in the galley are not part of that.
Able Seaman (AB)
Leading Seaman (LS)