The Dynabook concept described what is now known as a laptop computer or, (in some of its other iterations) a tablet PC or slate computer with nearly eternal battery life and software aimed mostly at giving children unlimited expression opportunities with all digital media imaginable. Adults could also use a Dynabook from the start, but the target audience would be children, and the software would grow up with them.
Alan Kay was the main proponent of the Dynabook concept. When Microsoft came up with its tablet PC he was quoted as saying "Microsoft's Tablet PC, the first Dynabook-like computer good enough to criticize."
Kay wanted the Dynabook concept to embody the learning theories of Jean Piaget and some of what Seymour Papert was proposing in order to apply Piaget in the field of computers. The hardware on which the programming environment ran was relatively irrrelevant.