mjhjmtu

I learned that from an instruction:

Co-processing does two things at the same time. It spawns a subshell in background mode and executes a command within that subshell.

[root@iz2ze9wve43n2nyuvmsfx5z ~]# coproc ( sleep 10; sleep 2 )
[1] 32508
[root@iz2ze9wve43n2nyuvmsfx5z ~]# jobs
[1]+ Running coproc COPROC ( sleep 10; sleep 2 ) &

When I refer to its manual, get an error as feedback

root@iz2ze9wve43n2nyuvmsfx5z ~]# man coproc
No manual entry for coproc
[root@iz2ze9wve43n2nyuvmsfx5z ~]# coproc --info
[1] 32579
[root@iz2ze9wve43n2nyuvmsfx5z ~]# bash: line 25: --info: command not found

[1]+ Exit 127 coproc COPROC --info

help works

[root@iz2ze9wve43n2nyuvmsfx5z ~]# help coproc
coproc: coproc [NAME] command [redirections]
 Create a coprocess named NAME.

 Execute COMMAND asynchronously, with the standard output and standard
 input of the command connected via a pipe to file descriptors assigned
 to indices 0 and 1 of an array variable NAME in the executing shell.
 The default NAME is "COPROC".

 Exit Status:
 Returns the exit status of COMMAND.

This's very confusing,

How could I have a big picture of the commands on which manuals I can reach to? How to distinguish them?