I was asked this question but didn't know what it does. I know chmod and its usages but what does this exactly do ?
Change permissions for file
http://www.ss64.com/bash/chmod.html - Man pages are our best friends.
In general chmod refers to change mode you can use alpha method to change folder permissions
Alpha method: Using alphabets (w, x, r, u, o, g, a, -, +, =, s, t) to change permissions for a file/folder
the command allow you to write access for all users and execute access for other users in file's group