|MadSci Network: Astronomy|
None of these things is really easy to understand, and all are subjects of on-going research, but the difference is easier to explain. All the time, no matter how active the sun is, there is a wind of charged particles blowing off of it. This is called the solar wind. It is a relatively low-energy product of the sun, and its only major effect on us here on Earth is to shape out planet's magnetic fields into a tear-drop shape instead of a ball. Sometime we observe sudden, very localized explosions on the sun where hot plasma (a very ionized gas) will get shot up from the surface. These are flares, and are much more common around the sun's active maximum in its 11-year cycle. Flares also appear to have little affect on us here on Earth (accelerate particles off of the sun completely, which may then hit the Earth's polar regions, thanks to our magnetic field, but this is a minor result). Finally, coronal mass ejections, or CMEs, are when a bunch of plasma on the sun suddenly becomes bouyant and lifts off of the sun. Typically, CMEs travel faster than the solar wind, so the drive a shock wave ahead of them (like a supersonic aircraft does). When a CME or the CME's shock hits the Earth, we often have geomagnetic storms. These can result in beautiful aurorae, as well as damage to satellites and ground-based electronics. So CMEs are quite important to us here on Earth (and even more so in Earth orbit). CMEs are sometimes seen with flares, but not always. They are not caused by flares, however. I hope that that clears up the difference. I'd recommened a good resource on this matter, but unfortunately the introductory-level textbooks on astronomy do not seem to have yet understood the importance of CMEs (it was only in the past 10 years that CMEs and not flares have come to be thought of as the cause of geomagnetic storms). Still, you might try Chaisson and McMillan's "Astronomy Today" or Seeds's "Horizons" for more information on flares and the solar wind.
Try the links in the MadSci Library for more information on Astronomy.