Q: sellor と vendor と bargainor はどう違いますか?

Let me add a few more vocabulary words.

First, the is the manufacturer. The manufacture creates the goods and products etc etc.

The manufacture usually sells these products to the vendor.

The vendor - also called a distributor then distributes these products to the seller.

A vendor usually sells to a seller/trader on the streets.

The seller is the store or person who sells to everyone/everybody.

These are all business/trading vocabulary. People usually call the seller by their store.

Let’s go to the store.
Let’s go to the supermarket.
Let’s buy some food from the food truck.
I think that vendor sells hotdogs.
I think that food cart sells hotdogs.

I also want to share with you one of my learning ideas. When you don’t know the difference between something, you can go to baidu and search images.

Baidu search: Food truck, vender, food cart

As for the last one, a bargainer is someone who bargains (tries to get the lowest price)

100 yuan? too expensive, 30 yuan. He’s a good bargainer. People also say. He’s a hard bargainer.(to buy or sell from) He drives a hard bargain. - meaning- he bargains very strongly, he is hard to negotiate with.

A bargainer is not a job though. If your job is to bargain then you are a negotiator. (US/China Trades negotiator, hostage negotiator )

But in trading, usually there is no job called a negotiator or bargainer, there are purchasing managers and salesmen.

A purchasing manager’s job is to negotiator to buy at the lowest prices. (sometimes his job is to find vendors as well)

A salesman’s job is to sell at the highest price. (usually he sells to the sellers or vendors)

So, the manufacturing company hires purchasing managers and salesmen.

The purchasing managers buy everything at the lowest price possible.

The purchasing manager might find some vendors.

The salesmen will then sell to the vendors or distributors.

The vendors and distributors will sell to stores and street traders. (or even stores selling on the internet- also called e-commerce)

e-commerce = electronic commerce
commerce = trade, buying/selling, general business activity

If I made any mistakes, or you have any questions, then feel free to let me know.