Hey there little buddy, do you know what happens when you ride a bumpy road on your bike and it shakes and rattles you? That's kind of like what happens when machines cut and shape things. Sometimes it can make the machine jiggle and shake a lot, which we call machining vibrations.
Now, you know how your parents probably taught you to hold your cup with both hands when you're drinking something so it doesn't spill? Machines also have to be held in place so they don't shake too much and mess up the things they're cutting. When a machine shakes too much, it can make the surface of the thing being cut rough or uneven, or even break the cutting tool.
There are different things that can cause machining vibrations, like the type of materials being cut, the shape of the tool or the speed of the machine. Sometimes, people have to use special tools or techniques to prevent the machine from vibrating too much. It's important to keep the machine stable so that it can cut the thing being worked on exactly as it's supposed to.