Okay kiddo, do you know what barbecue is? It's a yummy sauce that people put on meat like chicken, ribs or pork. Well, some people thought, why not put that sauce on another yummy thing: spaghetti!
So, they cook the spaghetti noodles in boiling water just like normal, and drain them when they're done. Then, they mix the noodles with the barbecue sauce until they're coated all over. And sometimes they'll add some extra ingredients like onions, peppers, or even bits of meat.
Once it's all mixed up, they serve it hot and you eat it just like regular spaghetti, but with a sweet and tangy barbecue flavor! Yum!