A dvd camcorder records to a tiny "dvd"
Mini dv records to a small "mini dv" tape, and you can usually use a firewire (or usb) to play back and upload the footage onto your computer.
Harddrive records to a built in hard drive disk, similiar to a harddrive on a computer.
High definition is exactally that.. HIGH DEF.. which is better quality, but won't make much of a difference if your playing it back on a regular tv set.
Point & Shoot just means that it's easy to use, no messing with manual settings, everything is automatic.
Hi-8 is an old format, not the best of quality but not the worst, certainally cheap though. Don't know if they even have firewire or usb ports to upload to computers, but the newer ones probably do.