Exoplanets are planets around other stars. NASA has just announced the probable discovery of another 1000 or so exoplanets. Five or so may even be like the Earth but we will not know much about them for a few years yet. Why is this important? Finding other Earth-like planets is likely to change our view of the universe. Until recently many felt that our planet was unique - now it seems that it may be far from that. From Scientific American:
"A newfound planetary system has six worlds, five of which rank among the smallest known, and the list of unconfirmed candidates has swelled to four figures"
"...it will be a few years yet before Kepler is able to identify a true Earth analogue—a small planet on a one-Earth-year orbit around a sunlike star."
"Astronomers have identified some 54 new planets where conditions may be suitable for life." - BBC