When you have a big task to do, sometimes it's easier to ask for help from other people. Work stealing is like that – when you have a really big job to do on a computer, sometimes it's helpful to ask other parts of the computer to help you out.
Imagine you have a big box of toys to clean up. You start putting the toys away in the toy box, but then you start to get tired. You ask your little sister if she can help you. She takes some toys and starts putting them away in a different toy box. Now the cleaning-up job is going faster because you're working together.
In the same way, work stealing helps make big computer jobs go faster. When a computer's processor is working on a big task, sometimes it gets stuck and can't move forward. Work stealing allows other processors to step in and help out, taking on part of the job while the first processor rests or moves on to a different task. This makes the computer work more efficiently and gets the job done faster.