What is the difference between addy and a REIT?

Is addy a REIT? No.

A REIT lets you invest in a "basket" of properties while addy lets you choose the specific address that you are investing in. More on the differences here.

An analogy we like is:

REIT = Music Album

addy = iTunes

With addy, you can pick and choose the specific song (ie. address) you want!