crontab(1), crontab(5) what's the difference?

Question

I want to learn how to use crontab. I see there are two manual pages:

 crontab(1)
 crontab(5)

Why are there 2 manual pages? What are the differences between them? Do I need to study both in order to use crontab, or is one authoritative?

Answer 1

crontab(1) is the man page of crontab command.
crontab(5) is the man page of crontab file.

The man pages are divided in sections as described in What do the numbers in a man page mean?. Each section groups similar man pages. For example, Section 1 holds user commands (commands runable by all users in the system). Section 8 covers SysAdmin commands (i.e. the commands that demand root access to be run). Section 5 covers file formats. See the link above for more info.

Another example would be passwd(1) which describes the passwd command, and passwd(5) which describes the /etc/passwd file format.