When I think of a farm, I always think of a big plot of land with cows or vegetable crops, but in Korea, farms can be anywhere. Here, they call them parks! Many houses don't have front yards, so if they have any amount of land, they plant things like cabbages and onions.
I think what makes Korean "parks" so special is that they are everywhere! I live in a town set in the countryside, so everyone there farms! It's not the same in the city, where there just isn't the room to grow vegetables in front of your house.
Since Korea has a lot of mountains, in these areas they can't build houses as close together as they can in the city. There are also just less people in the country areas, allowing for more space between the homes. This leads to houses having small plots of land that people like to farm on.