First, Blu-ray players can play all kinds of discs (Blu-rays, DVDs, CDs, MP3s, etc.), but conventional DVD players cannot play Blu-ray discs.
Second, to watch a Blu-ray disc, you need a high-definition TV with High Definition Multimedia Interface (HDMI) or Digital Visual Interface (DVI) inputs. All HDTVs of the past few years have these inputs; many from the early days do not. You also need to buy an HDMI or DVI cable to connect the Blu-ray player with the TV. The cable is a single strand that carries the extremely high bandwidth for the audio and video signals. (The cables that cost $10 or $20 are perfectly adequate.)
Third, ideally, your high-def TV should have a resolution of 1,080 p. Most of the newer models do; many of the older ones don't. Blu-rays will still tend to look better than DVDs on TVs of 1,080 i or 720 p resolution, but the difference won't be as big.
Fourth, again ideally, you should have a surround-sound speaker system hooked up to a multichannel audio-video receiver. Blu-ray discs also tend to have much better (uncompressed) audio. You can listen to the discs through the speakers on your TV (or a stereo speaker), but you won't get this dimension of "the Blu-ray experience."
Finally, Blu-ray is no longer the geeky medium it was when I wrote aboutthe Godfather reissues three years ago. You can buy a very good Blu-ray player for $200, retail. Almost all new home-video releases these days, both from the major studios and from "boutique" brands like the Criterion Collection, come out in both DVD and Blu-ray. According to Ronnee Sass, publicist for Warner Home Video, about 30 percent of its sales these days are in Blu-ray discs, and the figure is rising.