What is Cloudlet, how is different from Cloud?

[ashlee]

A cloudlet is a new architectural element that arises from the
convergence of mobile computing and cloud computing. It represents the
middle tier of a 3-tier hierarchy: mobile device --- cloudlet ---
cloud. A cloudlet can be viewed as a "data center in a box" whose goal
is to "bring the cloud closer".

[dgdheeraj]

Hi @ashlee ,
I've been trying to understand edge computing and it may be silly, but I have several doubts
So Openstack++ is the modified version of OpenStack Kilo.
Does OpenStack++ have to run on all the cloudlets apart from the main cloud or it has to be installed only on the cloud?
Cloudlet is used to offload compute. Then is the storage in the cloud?
And how secure are the cloudlets right now?