Find Identify User id Group id in Redhat Rhel5 Linux

In the Linux Operating system.All the users and Groups identify by separate unique Numerical Id.Linux Operating system root userid and group id as 0.user id group id zero 0 refer to unlimited access Full permission to the system.and if add any other user there userid and group id start from the 500.
[root@sourcecode~]# tail -n 6 /etc/passwd
opensource:x:500:500:opensource:/home/opensource:/bin/bash
user1:x:501:501::/home/user1:/bin/bash
rhel6:x:503:505::/home/rhel6:/bin/bash
rhel7:x:504:506::/home/rhel7:/sbin/nologin
rhel55:x:502:504:version5:/home/rhel5:/bin/bash
bash:x:505:507::/home/bash:/bin/bash
And we can identify the users id separately.
By the following command

[root@sourcecode~]# id username

[root@sourcecode~]# id rhel5
uid=502(rhel5) gid=504(rhel5) groups=504(rhel5),503(redhat)

[root@sourcecode~]# id rhel7


uid=504(rhel7) gid=506(rhel7) groups=506(rhel7),503(redhat)


[root@sourcecode~]# id root


uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),105(pkcs11)