Okay, so do you know how you have a computer or a TV and you can see things on it? Well, VESA is a way to help you attach your TV or computer screen to a stand or a wall mount.
You see, sometimes when you buy a TV or a computer monitor, it doesn't come with a stand or a wall mount. That's when VESA comes in handy. VESA is actually short for Video Electronics Standards Association, which is just a fancy group of people who make standards for how things work in the world of electronics.
One of the things they made a standard for is how to attach a TV or computer monitor to a stand or a wall mount. They made it so that there are four holes on the back of your TV or monitor in a specific pattern. This pattern is the same on all TVs and monitors that follow the VESA standard.
When you buy a stand or a wall mount that also follows the VESA standard, it will have something called VESA mounts, which are just little pieces of metal that fit into those four holes on the back of your TV or monitor. Then, you can attach the mount to a stand or a wall and your TV or monitor will stay put!
So, to sum it up, VESA is a standard that tells TV and computer monitor makers how to make four holes on the back of their product in a specific pattern, and this makes it easy to attach them to stands or wall mounts that also follow the VESA standard.