Usually in UNIX there is also another bit that precedes this 9-bit pattern. You do not need to know about it, at least for the time being. The first column here shows the permission bit pattern for each file. The third column shows the owner, and the fourth column shows the owner group. By the time, the information provided by ls -l should be enough for you to figure out what each user of the system can do with any of the files in the directory.
Permissions take a different meaning for directories.
Of course, only the owner of a file may use chmod to alter a file's permissions. A mode specifies which user's permissions should be changed, and afterwards which access types should be changed. You might have encountered things like chmod 755 somefile and of course you will be wondering what this is. The thing is, that you can change the entire permission pattern of a file in one go using one number like the one in this example. Every mode has a corresponding code number, and as we shall see there is a very simple way to figure out what number corresponds to any mode.