What exactly is a Portfolio?

[Sean Tabor]

I've been investing in Real Estate for about eight years. I started with one home during the collapse while I was in the service. When I got out I started expanding my rental base one at a time. I now have 5 properties. I know the term "Portfolio" is a group of properties (or any other type of investments), but is there a specific definition? How does one create a portfolio. 

Basically what I'm asking is this: Do I sell all my properties in one LLC, making it one transaction, or do I sell/buy several deeds in one closing/multiple closings? If I combine three into one LLC's sale, how do we report sales prices to each property? How will it affect the values of my real estate two blocks down?