SGID & SUID & Sticky Bit

[Root @ Station home] # ll-D admins/
Drwxrwx ---. 2 root adminuser 1024 APR 9 admins/
[Root @ Station home] # chmod 1770 admins/
[Root @ Station home] # ll-D admins/
Drwxrwx -- T. 2 root adminuser 1024 APR 9 admins/
[Root @ Station home] # chmod-T admins/
[Root @ Station home] # chmod 2770 admins/
[Root @ Station home] # ll-D admins/
Drwxrws ---. 2 root adminuser 1024 APR 9 admins/
[Root @ Station home] # chmod-s admins/
[Root @ Station home] # ll-D admins/
Drwxrwx ---. 2 root adminuser 1024 APR 9 admins/
[Root @ Station home] # chmod 4770 admins/
[Root @ Station home] # ll-D admins/
Drwsrwx ---. 2 root adminuser 1024 APR 9 admins/
[Root @ Station home] # chmod-s admins/
[Root @ Station home] # chmod 7770 admins/
Drwsrws -- T. 2 root adminuser 1024 APR 9 admins/

Chmod # Ugo File
# = 1: Sticky Bit
# = 2: Set Group ID (SGID)
# = 4: Set User ID (SUID)

You can set or clear the bits with symbolic modes like U + S and G-S, and you can set (but not clear) the bits with a numeric mode.

Sticky Bit:
For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on World-Writable Directories like/tmp.

Set Group ID:
For directories, file created under the directory will have the same group as Father directory.

Set User ID:
For files, user can run the program with owner's privilege.

Ref:

Man chmod