On UNIX web hosting, every single file and folder stored has a set of permissions associated with it, which says who is allowed to do what with the file.  File and directory permissions can often be changed using your FTP software.

The most common permissions include:

400     r——–       files (won’t let you accidentally erase)
444     r–r–r–      files (lets everyone read)
600     rw——-     files (no one else can read or see files)
644     rw-r–r–      files
664     rw-rw-r–      files
666     rw-rw-rw-     files
700     rwx——          programs and directories
750     rwxr-x—          programs and directories
755     rwxr-xr-x          programs and directories
777     rwxrwxrwx     programs and directories