What is chmod 777?

To make it easy to understand, we can break it into two parts.

chmod: this command is meant to perform an action, which is to change the file permission.

777: All three users (owner, group, public) can perform all three operations (read/write/execute) on a file.

// computer only understands numbers.

No permission – 0
Execute – 1
Write – 2
Write and Execute – 3
Read – 4
Read and Execute – 5
Read and Write – 6
Read, Write, and Execute – 7

chmod 777, in other word that 7(owner)7(group)7(public) have read, write, execute permission.

You can also use the -R (recursive) if your targeted folder has sub-folders. E.g. chmod -R 777

Resources

http://www.surfsafely.com/file-permissions-what-does-chmod-777-mean/