Isolation and quarantine are terms used interchangeably but have slightly different meanings and intents when it comes to trying to control an infectious outbreak.
Isolation is for the people known to have acquired a disease.
If you are confirmed to be sick with a disease, it’s important to get you away from people who are healthy. It’s best to be placed in isolation to separate yourself from healthy people to prevent them from getting sick.
In hospitals, you know you’re in an isolation room just from how the air pressure is regulated lower than then the air pressure outside the room (or wing). When you come from the outside into an isolation room, the door is hard to open and when it does open, a rush of air is sucked in behind you to prevent any respiratory droplets from going outside of the isolation area.