Numbers can mean just about anything, but they can be broadly put in to 4 categories.
Bowl Shape, Year of Manufacture, Quality (grade of briar) and Patent number. Some makers use all of these (Dunhill being a classic example), some have a couple only and others have none at all.
Each manufacturer 'generally' sticks to the same formula. To make things a little more complicated some manufacturers even add letters to the numbers, but these 'generally' refer to the size of the bowl.
It'll take a fair bit of reading, but if you want to look up what your pipe numbers mean, I would recommend looking your pipes up on
Pipedia. If it is a recognised manufacturer it should be in there. Use the search box on the left.
Either that or post them here and between the members we should be able to tell you.