AliExpress is a branch of Alibaba group of companies, a Chinese based company that deals with the seller companies of China. They deal with all kinds of retailers from clothing to electronics and accessories and everything.

It was launched in 2010 by Alibaba who brought all the small-scale sellers under one roof. Thanks to this modern E-commerce site, through which we can make transactions from any corner of the world. 
Basically, the working of this site is very much similar to Amazon and eBay and the thing which makes it different from them is that the company on its own sells nothing while it just showcases the products of the Chinese sellers, on their e-commerce site. 

速賣通

速賣通是阿里巴巴集團公司的分支機構，阿里巴巴集團是一家中國公司，與中國的賣方公司打交道。他們與各種各樣的零售商打交道，從服裝到電子產品及配件。

它是由阿里巴巴於2010年推出的，該平台將所有小規模賣家都置於一個屋頂之下。借助這個現代化的電子商務網站，我們可以通過它在世界任何角落進行交易。
基本上，該站點的工作方式與Amazon和Ebay非常相似，而與之不同的是，該公司自己在其電子商務站點上僅展示中國賣家產品的同時不銷售任何東西。

https://yakkyofy.com/blog/aliexpress-and-other-chinese-ecommerce-en/how-does-aliexpress-work-heres-a-practical-guide/