Gamma-ray bursts are one of the universe's most intriguing and energetic events. The very first link in the article (marked "gamma ray burst") will describe these mysterious events insofar as we understand them.
I highly recommend the Imagine the Universe NASA website to adults and teens for its fascinating topics. Even those who know little of astronomy will enjoy the site.
If you have grade-school-age children, there is a NASA site for them too. It's called StarChild.
You may wonder why I'm recommending these sites. I don't work for NASA. I was doing some research for a detail for APOD recently and came across several astronomy-subject websites which were full of bad information; outdated, erroneous, misconceived, you name it. One site even named Titan as a moon of Jupiter!
Wolf-Rayet stars are bright, hot, luminous, and rare. Only about 200 are known to exist in the Milky Way. The brightest one is Gamma Velorum, magnitude 1.74. It is the only prominent one; all others are fainter than magnitude 5. It's fairly nearby at approximately 840 light years. It's too far south to see from most of the Northern Hemisphere.
A most peculiar Wolf-Rayet star