Okay, so "Make America Great Again" is a catchy phrase that some politicians use to try to get people to vote for them. They think that America used to be really awesome, but maybe they think it's not as good now. So they say they want to make it great again.
But being great means different things to different people. Some people might think America was great in the past when jobs were more plentiful and people felt like they could support their families. Other people might think America was great in the past because they felt like their beliefs and values were more important to other people.
So when politicians say "Make America Great Again," they're trying to appeal to people who feel like things aren't as good as they used to be. They're saying they have a plan to make things better and bring back that feeling of greatness. But it's important to remember that everyone has their own idea of what "great" means, so what one politician thinks will make America great might not be what you or your family or your friends think.