Many years ago there existed a gap between mobile PDA's and cellular phones.  The phone was essentially a mobile radio, and the PDA was a little computer that held all of your data, calendars, contacts, etc.

Then as time went on, the mobile phone absorbed most of these PDA functions.  The evolution of the phone turned it into a PDA with a cellular radio.  The PDA became a phone, and the phone became a PDA.  They are both the same thing now, branded as the new PDA.

No matter what you call it though, the point is that it is a versatile handheld instrument, used for communication with other people and machines (e.g. The internet).  This is the platform which will open access to computing in every corner of the world, and with it also, bring a piece of our software to empower people and their imaginations.