Direct manipulation interfaces are like toys. When you play with a toy you use your hands to move things and make things happen. Direct manipulation interfaces are just like that, but they are used to work with computers or other technology.
Imagine you have a toy car with wheels that you can spin and make it go around. With a direct manipulation interface, you can use your hand to move things around on the computer screen, just like you move the wheels on the toy car. You can click on things and drag them to where you want them to be.
Direct manipulation interfaces don't make you click on a lot of buttons or type in a lot of commands like you might have to do with other interfaces. You can just use your hands to move things and get things done. It's like playing with a toy, but the toy is a computer that can do all kinds of things.
In short, direct manipulation interfaces let you use your hands to make things happen on the computer, just like you use your hands to make things happen when you play with toys.