Alibaba, the platform, is essentially a B2B platform.

Alibaba, as a group, also operates these platforms:

T-Mall - online retailer, B2C

Taobao - B2C/C2C platform, similar to eBay.

AliPay - payment gateway for e-commerce, similar to PayPal

Ant Finance - provide micro credit facility to consumer

Alibaba Cloud - web hosting, cloud computing

Alibaba Film - Movie making and investment

YouKu - Online video sharing platform and web streaming, like YouTube+Netflix. Alibaba acquired the controlling stake in 2015.

Amazon, as a group, operate all of the above except for the B2B platform. Amazon has its own payment gateway but it is not as extensive as AliPay.

Both are diversified group, with extensive vertical integration of its core business. Alibaba started off as a B2B platform while Amazon started off as an online retailer. Today, both groups more or less operate in a similar way with more or less similar business strategy.