The Unix manual is divided into sections (http://en.wikipedia.org/wiki/Man_page#Manual_sections http://en.wikipedia.org/wiki/Man_page#Manual_sections). Section

The Unix manual is divided into sections (http://en.wikipedia.org/wiki/Man_page#Manual_sections http://en.wikipedia.org/wiki/Man_page#Manual_sections). Section 2 is for system calls. Specifying the section number allows you to disambiguate which section of the manual you want to look in if a man page exists in multiple sections (e.g., "man 1 write" vs. "man 2 write").