Okay kiddo, so you know how we live in the United States, right? Well, a long time ago the US didn't have all the states that we have now. They had to get them somehow, and that's called territorial acquisition.
One way that the US got more land was by buying it from other countries, just like when we buy a toy from the store. They did this with the Louisiana Purchase in 1803 when they bought a really big piece of land from France. It was like getting a big new backyard to play in!
Another way was by fighting wars with other countries and taking their land. This isn't a nice way to get land, and it's like taking someone else's toy without asking. But the US did this a few times, like when they took parts of Mexico in the Mexican-American War.
Sometimes the US just took over land that already belonged to Native American tribes. This was really unfair and not right, because it was like taking someone's toy when they were playing with it. But unfortunately, it happened a lot.
All of these things add up to the US having the land and states that we have now. But it's important to remember that it's not always good or fair to take things that belong to other people or countries. We should always try to be kind and fair to others.