When you use up all the space in your RAM, your computer has nowhere to store the data it needs to carry out its tasks. This is called Random Access Memory (RAM) and it stores all the data that your device needs to complete active tasks and run programs and processes.
Much like a brain, your computer has a chip on its motherboard that houses its short-term memory.
Once just an animal with horns, RAM these days is far more technical and can make or break your online and computing experience.