4a, 2b, 3c. You've probably heard these number-and-letter combos thrown around in the hair blogosphere lately, but in the words of Justin Bieber, "What do [they] mean?" (And you probably have that song stuck in your head now. You're welcome.) On the most basic level, it refers to a hair-typing system that helps you determine your texture to find the products and tools that are best for you. The system — which is often imitated — was originally established by Andre Walker, Emmy-award winning celebrity hairstylist and the man behind Oprah Winfrey's glorious curls. "In order to take care of your hair properly, you need to identify it. So I created the Andre Walker hair-typing system, which, at the time, was just a way for me to categorize hair," Walker tells Refinery29.You can check out an in-depth breakdown on the typing system here , but Walker's method essentially divides hair types into four separate categories: 1 refers to ladies with straight hair, 2 for women with wavier patterns, 3 for the curly girls, and 4 for those with tighter coils. Those numbers are then broken down into subsets. For example, 1a is someone with straight and fine hair, while 3b describes someone with corkscrew curls, versus looser ones. It's important to recognize that the typing system isn't for everyone. Some women claim that it's confusing, divisive, and creates an unnecessary sense of hierarchy — and yes, those are valid arguments and to each their own. But for anyone starting out (whether you're going natural or just looking to understand your hair a little more), Walker's line and hair-typing system is an easy way to get your feet wet.Now, almost 20 years after introducing the chart, Walker is coming out with a brand-new line of hair-care products that serves as an extension of his typing system. "Each hair type is different — there are certain products that you would use on straight hair that you probably wouldn’t use on kinky hair," says Walker. "That’s why I’ve broken it down into four categories and also recommend which products to use for each hair type.”The newly improved collection, which includes everything from sulfate-free shampoo to straightening creams, all have one ingredient in common: Mongongo oil. “Mongongo oil is an oil that people in Africa have been using on their skin and hair for over 100 years or more. It’s really high in nutrition [and] very high in vitamin E, which is great for skin and hair."