Question about Loan Officer job options (commission, mortgage, mortgage, sales)

[Toxic Toast]

Hello Real Estate Professionals. I have a question that I am hoping you all might be able to help with. I am interviewing with a company on Wednesday morning, and have no experience in the field what so ever. I am a recent college graduate looking for entry level work. If anyone in the Indianapolis area wants to know who or has heard of them, that would be nice to find out too, but I would rather private message that; I do not want this coming across as an advertisment; esp if they do not hire me.

So anyway, they describe the company as this:

We are a mortgage broker that connects home buyers and home owners with financing options. We are looking into obtaining a real estate brokerage license and adding a real estate sales division to our office.

And the position is described as this:

(name of comapny) is now hiring Full Time and Part Time Loan Officers!

Experience Preferred
Commission Tier up to 75%
No desk fees

Work from your home or our office.
Applicants outside of the Indianapolis area (within Indiana) are welcome to apply!

So, without further adu, here are my questions I am hoping someone can address:

1) What exactly does a loan officer do?

2) What exactly does that "commision tier" mean?

3) What purpose does a mortage broker serve? Do a lot of real estate professionals or companies rely on loan officers and mortgage brokers?

4) I have no experience in this field; but I did recently graduate with an Economics degree. How can I spin this into a positive thing to make myself hire-able?

Thanks, and I hope you all can and are able to help!