Its not really any different than any other POS coin, only difference is you get rewarded more if you actively use your account.
I read this on the website but still don't fully understand-
What is this "POI"?
POI is short for "Proof-of-Importance". It is a consensus algorithm at the core of the NEM software. The higher your importance, the higher your chance to be allowed to calculate a block (and harvest the fees inside that block). POI adjusts your importance depending on how many transactions you make, with whom you make them and a number of other factors. If you don't do any transactions POI will set your importance based on your balance only (it is then similar to proof-of-stake).
I also need to read more about "delegated harvesting".
It sounds like the ability to mine offline but I'm not totally sure.