One-class classification means you want to teach a computer to recognize if something belongs to a specific group or not. It's like when your mom asks you to find all the apples in a big pile of fruits. You know what an apple looks like, so you can pick out all the apples from the pile. That's one-class classification!
In computer terms, this means that you have a bunch of data (like pictures of different fruits), and you want the computer to learn what a specific type of fruit (like the apple) looks like. Once the computer has learned what an apple looks like, it can tell you if there's an apple in a picture, even if there are other fruits in the picture too!
But how does the computer learn what an apple looks like? Well, it looks at a bunch of pictures of apples that you give it, and it tries to find patterns in those pictures. For example, it might notice that apples are usually round and red or green, and they have a little stem at the top. Based on those patterns, the computer can start to recognize what an apple looks like.
Once the computer has learned what an apple looks like, you can give it a new picture of fruits, and it will tell you if there's an apple in the picture or not. If there is, great! If not, maybe you need to look closer.
So, in summary, one-class classification is like teaching a computer to recognize if something belongs to a specific group or not. By showing it lots of examples of what that group looks like, the computer can learn to recognize that group and help you identify it in new data.