So, one time, way back in 1841, the United States of America made a law called the Preemption Act. This law said that if you were living or farming on government-owned land, and someone else wanted to buy that land, you could buy it first.
Basically, it was like a "right of first refusal," which means you get the first chance to buy something before anyone else can. And this law only applied to certain places, like places where the government owned a lot of land, so it didn't apply to everywhere in America.
Now, why did they make this law? Well, a lot of people were moving westward and settling on land that was owned by the government, and the government wanted to encourage people to settle in these areas because that would help expand America's borders.
But they also wanted to make sure that people who were already living on this land could keep living there and farming there, even if someone else wanted to buy the land from the government. So, they made this law to protect those people's rights to their land.
Basically, the Preemption Act meant that if you were living on government-owned land, you had the first chance to buy it if the government wanted to sell it. This helped people keep their homes and farms, and it also helped America grow and expand to new territories.