Blu-ray players are THE high definition of dvd players. They are the only technology that actually broadcasts in your true 1080p resolution. The disk itself holds almost 6x the information of a standard dvd. The cool thing about them is that the blu-ray disks have an extra layer of protection on them that prevents scratching...so if you're like me and throw your dvds on your shelf and don't put them back in the case, that layer definitely helps. The blu-ray players can play your standard dvds as well, but they bump up their level of quality too...so you don't have to go back and rebuy all your disks in blu-ray.
"HD Ready" refers to any display that is capable of accepting and displaying a high-definition signal at either 720p, 1080i or 1080p using a component video or digital input. It just means you can view high definition broadcasting.