The right rights…

chmod is the command and system call, in Unix-like operating systems,which may change the access permissions to file system objects (files and folders).

chmod 755 /var/example/ will set 755 (drwxr-xr-x) on /var/example/

chmod -R 755 /var/example/ will set 755 (drwxr-xr-x) recursively on /var/example/ and his content.

Take a look on wikipedia.org / Chmod or, on you system chmod --helpman chmod

Use the ls command.

ls -l /var/list all files and directory in /var/, the -l is to show rights, weight (...) and others informations.

Take a look on the help or the manual for more informations (RTFM).ls --helpman ls

Nope, not really, there are some options to chmod we didn't see with this tool. For more information, you can check some good source like
wikipedia.org / Chmod, wikipedia.org / File_system_permissions

Yep, there may be one other digits coming first, like 755 become 0755. Depends of sticky, SUID -setuid- and GUID -setgid-, take a look on the next point of this FAQ.

Yep, there may be other letters when you look at the rights of your files and folders.

• The first letter, other than -
  • d--------- is for a Directory.
  • l--------- is for a symbolic Link.
  • c--------- is for a Character special file.
  • b--------- is for a Block special file.
  • p--------- is for a FIFO (Pipe).
  • s--------- is for a Socket.
• ---------t---------T Sticky Bit, short story, this right disallow any right to delete a file, wathever the parent directory rights, if the user who want to delete the file is not root or the owner of the file. wikipedia.org / Sticky_bit.
• ---s---------S------------s---------S--- are about SUID -setuid- and GUID -setgid-, this are some specifics rights allowing to "bypass" some rights with the rights of a the owner or the group. Take a look at wikipedia.org / Setuid for a better explanations.