A hypernova is just a really, really big supernova. UMass has a (tacky designed) web page that explains it.
A hypernova explosion typically has a mechanical energy output of ~ 10^53 ergs, or about a factor of 100 greater than a supernova.
Regarding aftereffect, the page says this:
The age of the hypernova remnant NGC5471B is about 30 thousand years, while the age of MF83 is about 1 million years.
As best as I am able to determine, we have not had a chance to observe any hypernova candidates in the modern era, although APOD featured the same one as mentioned by UMass:
According to New Scientist, research suggest the upper limit to a star is about 150 solar masses. These are the stars that create the infamous supernovas.his is as derived from the Eddington Limit. Although R136a1 is an example of a star at nearly double that. It is believed that these monsters are what are responsible for hypernovas. There is much to be learned from these stellar monsters!