What does aboard mean?!

What does aboard mean?

I was reading a reading i had done and it said something about being aboard what does that mean ?

I believe "aboard" comes from "on board" which has nautical roots. Being "on board" firstly means you are on the ship or boat (which used to always be made of wood. ie. on board). But it also means you have joined other people in purpose/direction.... not much different from it's nautical roots considering people on a ship also have a unified purpose and direction.