The US retail giant is acquiring Jet.com in part for its rapid ascent; it hit $1 billion in sales and 12 million stocked items in just a year. Walmart, by contrast, has seen online sales growth decline in five consecutive quarters. It adds that the acquisition will bring "fresh ideas and expertise, as well as an attractive brand with proven appeal, especially for millennials."

Walmart.com [will focus] on delivering the company's everyday low price strategy, while Jet will continue to provide a unique and differentiated customer experience with curated assortment.

Jet CEO Marc Lore knows Amazon well, having sold his last company, Quidsi, to Jeff Bezos' firm for $545 million in 2010. Lore owns 25 percent of Jet and will continue to lead it under Walmart, according to reports.

Jet will operate separately from Walmart's online business. "Walmart.com [will focus] on delivering the company's everyday low price strategy, while Jet will continue to provide a unique and differentiated customer experience with curated assortment," according to the release. Lore points out, though, that Jet will obviously benefit from Walmart's "purchasing scale, sourcing capabilities, distribution footprint and digital assets."