Pre-existing conditions were an insurance industry term for different medical conditions that people already have when they’re shopping for a new plan. These could range from pretty basic things (like asthma) to more serious conditions (like cancer). Before Obamacare, health plans could deny coverage — or charge higher prices — to people who had them.
Under Obamacare, the concept of pre-existing conditions no longer exists. Insurance companies are barred from asking questions about applicants’ health status. They can only factor in three things — age, location, and tobacco use — in setting a shopper’s premium rate.
This is why insurers believe the individual mandate is so important: they worry that if healthy people don’t have to buy health insurance, and if insurers can’t turn away sick people, then too many sick people and too few healthy people will sign up.