It's the type of man
page. man
's manuals are split into several sections, chapter 1 is for executables, and git
is an executable. The whole list is given by man man
:
1 Executable programs or shell commands
2 System calls (functions provided by the kernel)
3 Library calls (functions within program libraries)
4 Special files (usually found in /dev)
5 File formats and conventions eg /etc/passwd
6 Games
7 Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7)
8 System administration commands (usually only for root)
9 Kernel routines [Non standard]
Some things are in multiple sections, like time
is both a command and a system call, see the difference between man 1 time
and man 2 time
.