If you go aboard a ship or plane, you go onto it or into it.
It had taken two hours to load all the people aboard.
用了两个小时才让所有的人上了船。
If you are aboard a ship or plane, you are on it or in it.
She invited 750 people aboard the luxury yacht, the Savarona.
她邀请了750人登上“萨瓦罗纳号”豪华游艇。