Okay kiddo, you know how when you play with play-doh and leave it out in the sun, it gets all dry and hard and you can't mold it anymore? Well, that's kind of what happens to some plastic materials called polymers when they are exposed to different things like heat, sunlight, or chemicals. They start to break down and become brittle and weak.
That's where stabilizers come in. They are like little helpers that protect the polymers from getting damaged. Stabilizers can come in different forms, but they all work to prevent the polymer from breaking down. Some stabilizers absorb the harmful things that would damage the polymer, like a sponge soaking up water. Others create a barrier between the polymer and the harmful thing trying to affect it.
When the polymer is protected by a stabilizer, it stays strong and flexible even when it encounters things that would normally damage it. This means that it can be used for longer periods of time without needing to be replaced. So just like how you use sunscreen to protect your skin from getting burned in the sun, stabilizers protect polymers from getting damaged.