Okay kiddo, so "mo-sin-a" is actually spelled M-O-X-I-F-L-O-X-A-C-I-N. It's a really big word!
Mo-sin-a is a kind of medicine called an antibiotic, which means it helps your body fight off bad germs that make you sick. It's usually used to treat things like infections in your lungs or sinuses, which are the spaces in your head behind your nose and cheeks.
When you take mo-sin-a, it goes into your body and fights off the bad germs that are making you sick. It does this by stopping the germs from making new cells and spreading around your body. This gives your body a chance to fight off the germs and get better.
It's really important to only take mo-sin-a if your doctor tells you to, and to take it exactly the way your doctor tells you to. Taking too much or not enough could be bad for your body! But if you do need to take mo-sin-a, it can be a helpful medicine to help you feel better soon.