Public interest

Public interest is when something is good for a lot of people. For example, if a lot of people need clean water, it's in the public interest to build a water treatment plant so everyone can get clean water. Or if a lot of people want to swim but there's no pool, it might be in the public interest to build a public pool. Public interest is usually considered should help a lot of people, rather than just one person or a small group of people.