How do you call this job in English?
How do you call the department or the place where you can buy TV, audio systems, computers, cameras, etc in a mall or big shop?
Guess this. If in that department there is a person (not worker of the shiop) who is an expert in an specific brand and invite the people to test the products of his brand and the people ask him about specification on this or that product of his brand. He is representing the brand there. What's the name of that job.
The last question. In Spain you can work for a company or there is a second option where you can work by yourself(you can issue bills, etc..). How do you call this people or job?

Thanks

Question

How do you call this job in English?
How do you call the department or the place where you can buy TV, audio systems, computers, cameras, etc in a mall or big shop?
Guess this. If in that department there is a person (not worker of the shiop) who is an expert in an specific brand and invite the people to  test the products of his brand and the people ask him about specification on this or that product of his brand. He is representing the brand there. What's the name of that job.
The last question. In Spain you can work for a company  or there is a second option where you can work by yourself(you can issue bills, etc..). How do you call this people or job?

Thanks

Answer

1. We'd call that an electronics store. 
2. That sounds like a representative. For example, I might say there's an Acer representative in Best Buy (an electronics store). I can't think of a more specific word than that. Sometimes this is shortened to "rep".
3. Do you mean people who are self-employed?