Alibaba wants to compete with Amazon in shipping
Arguably, this is the one real strength Amazon currently has, as it's catalog seems less and less impressive.
Alibaba already has good warehousing and distribution, as shown in how it handles China's 'Singles' Day.'
Ali also has a payment company and other businesses that help speed up shipping.
For delivery, Ali depends on partnerships with airlines and ground-based delivery co's (DHL).
Ali wants to expand the products it offers to its 190 countries and charge $3 per year for fast (like 2-day) shipping. Amazon currently charges between $13 and $130 per year, depending on location (India, UK).
Ali's product prices are comparatively cheaper than Amazon, because Ali has direct access to the Chinese producers.
Ali sells a lot of alleged counterfeits, though, which hurts the real companies. Amazon also has faced these criticisms, but less so.