"Push control" and "pull control" refer to opposing marketing strategies. In a nutshell, push control entails taking a product to customers, while pull control involves getting customers to come buy the product from you.
Push marketing relies heavily on manufacturers making their products visible and having abundant supply. In stores, push marketers' wares need to be strategically displayed to catch customers' eyes. Push companies might also employ people to hand out free samples or discount coupons. Subtler strategies include placing the "pushed" product next to a complimentary item (e.g., a display featuring a new brand of breakfast cereal beside the milk section). Online, push marketing includes tactics such as offering special internet discounts, highlighting positive customer reviews, and using professional photography that makes a product (or service) alluring. On social media, it may include having an "influencer"—a celebrity with many followers—endorse (or even mention) the new product. An example of push marketing would be when a beverage company releases a new type of soft drink. It needs to get the drink into stores, ensure its warehouses are well-stocked, alert customers that the new drink is available, and then convince them to buy it.
Pull marketers, conversely, operate on the premise that customers will come to them—due to their company's superior prices, service, convenience, brand awareness, market dominance, or some combination thereof. They generate buzz for a new product with advance advertising, trade-show prototypes, media coverage, and word-of-mouth hype, so that when customers come into their stores or visit their website, they are excited and ready to buy. Online, a pull marketing website might feature articles educating visitors on finding a product that fits their lifestyle, links to media reports that promote their product, and slick videos promoting their brand. A classic example of pull marketing is Apple stores (followed swiftly by Microsoft stores). Both companies annually promote new products and update current ones, creating steady traffic streams into their shops. But people come in not just to buy. They can also try out products, get repairs, purchase accessories, and sometimes just to hang out and play screen games. Starbucks is another good example of a business that "pulls" people into its stores, which it markets as a "third place" to relax, aside from home and work.
In reality, of course, most companies use a combination of push and pull marketing strategies. When Apple releases a new iPhone, it needs some push marketing to get the phone into its stores and other retail outlets, and pull marketing to draw buyers into the stores. If the quality of the new phone fails expectations, it hurts the brand and will "pull" fewer customers into stores.
For more information, here are a couple of good websites on the topic: