Djent is a relatively new term to most mainstream rock music listeners. It's a onomatopoeic term that describes the sound an electric guitar makes, but the genre takes it to a whole other level.
Meshuggah is considered to be the pioneer of the genre. Djent is progressive metal that uses unconventional time measures and uses the guitar sound to give it the sheen of heavy that it displays on each and every song.
In this entry, apart from simply mentioning what it comes from, I'd like to recommend a few Djent bands to listen to.
After shows with Dream Theater and Fair to Midland, Periphery seems to be the band primed for the most success. Misha "Bulb" Mansoor created the band out of his own musical productions on guitar searching for the perfect vocalist before finally going with Spencer Sotelo in 2010.
Vocals, while present, don't seem to always be the main attraction in Djent as is the case with Animals as Leaders, an instrumental metal band that toured with Underoath and Thursday amongst others.
Djent hit the US, but its effect is largely felt overseas as well.
TesseracT has largely been put on a lot of the same tours that the previous two mentioned have been on. While they're not seemingly as popular as the other two, they seem to be growing steadily in the same direction. I've started to get into this band quite heavily myself in the last couple of months.
Finally, one Djent band that hasn't fully started that should be big in 2012 is Being, which is being produced by two Periphery members, one current (Misha Mansoor) and one former (Chris Sabol).
While there are specific characteristics of Djent, the bands and the differences between them are different enough that there's something for every metal fan.
Check 'em out!