Jquery Mobile is like having a magic wand that can turn any website into a pretty and easy-to-use mobile app. It's like when you play pretend and turn a cardboard box into a spaceship - Jquery Mobile does something similar, but with your website.
It works by creating special code that understands how to work on your phone or tablet, so you don't have to do all the work yourself. It's kind of like when the grown-ups use shortcuts in the kitchen to make a big fancy meal, but only have to do half the work!
Jquery Mobile also helps make things easier for you when you're using your phone or tablet to look at a website. It knows to make buttons bigger so you can press them with your fingers, and it makes sure everything goes in the right place so you don't have to zoom in and out all the time.
So, imagine having a boring old website and then poof, Jquery Mobile turns it into a fun, easy-to-use app that you can play with on your phone or tablet. Pretty cool, huh?