How ebay work?

Hello everybody
1.i have some question about EBAY sell / buy structure .
i want to know why for example EBAY sell DELL laptop while DELL website have online selling ?
it would be great if anyone give some reference too .
TKS

There are lots of stores on the street selling Dell computers. So, a retailer buys the computers from Dell and then sells them to you in their shop. Ebay is an online version of the street shop. Anyone can set up an Ebay store and sell goods that way, rather than through a physical store. Is that what you are asking?

1.thanks ralph but maybe i did not a clear question
yes you are right but if you mention on ebay and dell you will understand in some times they have a different price for one item !?
why should this happen ?
2.and if we supposed dell and ebay have a same price for one item why a buyer should buy from dell ?

If I understand you rightly, I think you are describing what’s known as the marketplace. People sell things cheaper than others to get the sale.

if we supposed dell and ebay have a same price for one item why a buyer should buy from dell ?

Buyers will choose what’s most convenient for them. Dell might offer better warranties or service, which might make a buyer choose them over Ebay.