Walmart (NYSE: WMT) has been impressing investors recently, with shares up about 15% since June 1. While much of the enthusiasm toward the stock is tied to a strong second quarter, another notable narrative at the company is its progress in e-commere, including strong double-digit growth in e-commerce sales and Walmart's investment in a leading e-commerce marketplace in India.E-commerce still only represents a sliver of the company's overall business.