Okay, so imagine you got a pack of crayons and a piece of paper to draw on. Now, you have a friend who has a toy that they really love but you don't have one like that. So you ask your friend if you can borrow it but they say "no". You really want to play with that toy, so you start crying and feel really upset. That's kind of what smoking is like.
Smoking is when people light up these sticks that have tobacco in them and breathe in the smoke. Tobacco is a plant that has a chemical called nicotine in it, which makes people feel really good for a short time. Just like how playing with that toy would have made you feel happy, smoking makes people feel good too.
But here's the thing, smoking is really bad for your body. It can make you sick and even cause cancer which is a really serious disease that can make people die. It's like eating too much candy, it might taste good at first but it can make you really really sick over time. And just like how you couldn't have that toy, it's better to not start smoking at all so that you can be healthy and avoid getting sick.