It used to be thought that muscle was built in the 8-12 rep range, with 4-6 reps being for strength and 12+ being for endurance. However, research is showing that this is not the case. While low reps are superior for strength, and high reps superior for endurance, the truth is that any rep range can build muscle when sets are taken to, or close to, failure.
I actually prefer to do most of my training with high reps. While they may not be superior for building strength, they are excellent for building work capacity, endurance, volume tolerance and burning fat.
https://www.ncbi.nlm.nih.gov/pubmed/28834797