If you read through Unix like documentation you come across this notation logrotate(8) or find(3). What does the (8) mean?

The number represents the section assigned to a given man page for a command. The different numbers are:

1. General commands
2. System calls
3. C library functions
4. Special files (usually devices, those found in /dev) and drivers
5. File formats and conventions
6. Games and screensavers
7. Miscellanea
8. System administration commands and daemons

You can read more here: Unix Programmer's Manual