Clear the confusion in between SKU, SKU ID, UPC, EAN Code.

What is SKU code (or the SKU ID)?
The complete form of the SKU code is the Stock Maintenance Unit. This is a unique identifier code for a product to track and record the number of stocks of an item (among the other attributes). For example, if a retailer would like to know how much he has for small and medium-sized red shirts. Therefore, each one will have a unique SKU code assigned and its respective quantity in the warehouse. In terms of inventory tracking, one of the most used methods is to assign an SKU code or SKU ID for each product.
SKUs are unique items, such as products or services, because they are offered for sale and represent all attributes linked to items that distinguish them from other items. These attributes may include, among others, brand, size, color, manufacturer or warranty. Therefore, the code that stores all this information about an item gives you a unique stature in your inventory, which means that it is easy to track and remember certain items. In addition, because the code stores all relevant information about the article, someone who is skilled in reading the code can find out everything about the article without having to go and should check the "side of the box".
What is the importance of the SKU code in electronic commerce?
The SKU code is a critical part of electronic commerce. In e-commerce, a company generally sells on multiple sales channels such as Amazon Flipkart, Paytm, Myntra, Jabong, Snapdeal, Shopify, Magento, and others. Under omnichannel electronic commerce, they can also sell online from the inventory of their offline stores.
To identify the product as the same product in all sales channels and link it to the correct product in the store or in an offline store, the SKU code acts as the central identifier. There is a great need to keep the inventory synchronized across all digital e-commerce platforms so that the inventory is always up-to-date, the possibilities of exhausted orders are minimized and the sales potential is maximized by making all the inventory visible in all channels In electronic commerce, given that the volume of B2C orders is usually high and should be sent to disparate individual buyers. To accelerate the operations in the warehouse, a company must follow SKU codes with a barcode on the products instead of relying on the images or photos of the products to carry out the collection, packaging and shipping operations. When photos are used in warehouse operations, there is a high probability of sending incorrect products to customers, which generates expensive returns and product replacements. The use of SKU codes with or without barcodes ensures that the correct products are shipped.

What is SKU vs UPC vs EAN Code?
There are several other systems that combine coding products for tracking purposes,such as Universal Product Codes (UPC), EAN / IAN (European article numbers / international article numbers) or global merchandise numbers (GTIN), which use codes of numbered bars to identify with unique products in the database. It is based on global standards determined by the GS1 organization and has a default length and types of characters (for example, EAN-13 containing 13 digits and UPC-A contains 12 digits). These codes must be sent/applied and delivered to the requesting entity after the approval process. There may also be costs involved in the
process.
The main difference with SKU codes is that retailers are free to create their own SKU code and enter it into the inventory system without having to comply with larger tracking schemes or global standards. With SKUs, retailers maintain the length and flexibility of characters in the code. This way it gives them the ability to handle and control the size of their inventory, replace manufacturers or wholesalers without the difficulty of repairing the system by internally mapping their product SKU codes to their suppliers or buyers.