A coop is another word for chicken shed.
The roost is another word for perches where the chickens sleep at night.
They should not be sitting in the nesting boxes or upon the ground as they poo all night.
Every shed will have a different style of roosting rails, some use natural tree branches to aid foot health to such as preventing bumble foot. Other sheds will have straighter beams.
Some roosts are high and others are just up off of the floor.
Hope that helps out new chicken owners. Keep up the great questions. I love to answer them.
You never know, what you ask might be what someone else is wondering about, too.