Okay, imagine a big boat, which we call a ship. Just like how you need friends to play a game, a ship needs friends too! These friends are called a crew.
The crew is made up of people who help the ship to sail. Some of them steer the ship, which means they help it go in the right direction. Others take care of the ship, making sure it's safe and everything works well, like fixing things if they break or keeping the ship clean.
So, when people say 'Every ship has a crew,' it means that every big job, like sailing a ship, needs more than one person. Just like you need a team to play football or a group to build a big tower with blocks, a ship also needs its special team to work together and have fun on the water!