Bar codes are tricky. There are dozens of different kinds, each defined by the industry represented. Ultimately, the information and types of codes are maintained by the Uniform Code Council in Ohio. The basic purpose of a bar code is to make each item in a certain class (such as industrial or consumer products) completely unique. This makes it possible for the industry to track an item from production to delivery to sale. The two basic retail bar codes are the EAN-13 and the UPC. These contain information coded by the manufacturer.
Look at the length of the bar code number. If it is 13 characters, it is an EAN-13. If it is 12, then it is UPC. This is the main distinction between the two different retail codes. If it is UPC, it is made in the U.S. and meant to be sold in the U.S. If it is made abroad or meant to be sold abroad, it will have the EAN-13 code.
Look at the first number of the UPC. The UPC-A first number information has a few markers making the coding identifiable. The number 3 is for the National Drug Code. A 4 indicates it's used only by the store. The number 2 is for “random weight items.” The remainder are reserved for the manufacturer to code each item uniquely. More specific information is not obvious from the numbers and needs to be ascertained elsewhere.
Look at the first two or three numbers of the EAN code. If it has the EAN code, then these identify the country of origin or destination (see resources below for coding). The customs agency of the country of either origin or destination codes the item. Once the country is identified, the remainder of the code is identifying the type of product.
Call the Uniform Code Council. If you need further information on the specific coding for each individual item, only they will have it. Under certain circumstances, the manufacturer will also have that information, but since the council specializes in the coding information, they are a better bet.