“A sonnet is a fourteen-line poem,” Virmad says automatically, “usually constructed in so-called ‘mirrored’ form, with either a six- or seven-line pattern that’s then repeated in reverse, with — for a six-line pattern — a couplet called the ‘axis’ between the two patterns. There are a number of popular variations; most of them are associated with the Liozh, for obvious reasons, but there are sonnet variations associated with every faction, and, of course, some that are faction-neutral.”

[I'm going to add a bunch more info to the wiki.]