When a hillside is covered in trees soil and rocks are not washed away when it rains why is this?

Oh, dude, it's like nature's way of saying, "Hold up, let me protect this hillside real quick." So, when you have those trees chilling there, their roots are like, "Nah, rain, you can't take our soil away," and the rocks are just like, "We're gonna stick together, bro." It's like a teamwork thing, you know? So, the hillside stays intact and doesn't turn into a muddy mess.