Have you ever heard of a rule that says you have to clean up your toys before you can play with something new? Well, the government has a similar rule for companies that make electricity.
When companies make electricity, they often use big machines that burn things like coal or gas. This can make the air around the machines dirty and bad for people to breathe. That's why the government made a rule called the new source performance standard, which says that when companies build new machines to make electricity, they have to make sure it doesn't make the air too dirty.
The rule sets a limit on how much pollution can come out of the machine. It's like saying "no more than this many Legos on the floor" before you can play with a new toy. If a company doesn't follow the rule, they can get in trouble with the government.
The new source performance standard helps make sure that when new machines are built to make electricity, they don't make the air too dirty, which is important for everyone's health.