Evaluating purchase price of an office building

[Russell Gronsky]

I'm new to commercial real estate. I've only done residential in the past so bare with me. 

I saw a commercial building for sale in my area. I contacted the real estate broker to ask several questions about the property. I know each commercial property is unique but since this guy deals with commercial properties in the area for a living, I asked him what he has seen buildings similar to this one go for in the past. This was his response:

We have a market seller here but if I had to guess, I suspect this trades between an 8.5 & 9% cap rate

Can someone explain, in plain English, what this means? Do I have to pull up financials for the property again and do some calculations?

Thanks for the help.