Hey, I laughed. I'm not proud of it, but…
This is a parody of the usual musician-movie. Conner (Andy Samberg) is the lead rapper of a wildly successful boy band, the Style Boyz. And, as these folks tend to do, he breaks up the band for a solo career. Which fails spectacularly and hilariously as the pretensions and egotism of music world denizens are ruthlessly mocked.
There are a lot of cameos by Andy Samberg's Saturday Night Live colleagues. Also a lot of cameos from actual musicians; I assume I would have recognized them if I were 40 years younger. (I did recognize Justin Timberlake, though, and he's very funny with a small part here.)
It's R-rated for "some graphic nudity, language throughout, sexual content and drug use". The graphic nudity involves, um, male genitalia. As part of a joke.
Wikipedia says it was a box-office bomb: "grossed $9 million, failing to meet its budget of $20 million, despite positive reviews from critics." Ah, well. Andy probably overestimated the appeal of graphic male nudity.