When I started using computers, they filled a whole room. By the early years of this century they were much smaller, but you still couldn't carry them around. There were things like PDAs, but they were nothing more than glorified diaries. This was one of the first fully-functional pocket computers available outside Japan (some earlier and less fully-functioned models were only available there) and more importantly it was the first using the Linux operating system, meaning it was easy for its owner to write software to do complex things on it.
We now take things like iPhones for granted, but this, although it was never a mass-market seller, was a precursor to them.