Personal Clouds are still a fairly new concept which remains unexplored to a large extent. There are multiple types of cloud computing: public, private and hybrid. In a public setup, the applications or programs are hosted on a wide pool of physical resources thereby lending flexibility and scalability to your infrastructure.
In a public cloud, the pool of physical resources is shared by multiple organizations whereas in a personal cloud that’s not how it works. One typical example of a personal cloud is NAS based cloud storage. Imagine you have a NAS box in your organization which you have configured in RAID. Now you can make that NAS box available over the internet to secure users to have access to certain data as and when they want.
So in this way, the physical resources are also not being shared by multiple organizations as is the case with public clouds. You can decide which applications or programs to run on the cloud infrastructure and which peripheral devices would be allowed access to the same.
And the solution is entirely scalable, without having to share your resources with other organizations. In case of a public cloud setup, eg being Dropbox or Google drive, the services or applications are hosted on a virtualized platform over a pool of shared physical resources. However, in the case of a NAS based cloud setup, it is more of a private thing.