Linux servers have different possible file permissions which can be set on a file or folder. By default the permissions will be set to 0644, which allow you to read/write to the file but others will be only allowed to read the file.

Files such as cgi scripts need to be set to executable. A permissions of 0755 should be set to files which need to execute.
Some scripts may ask you to set a folder or file to permissions of 777. This is NOT recommended. Our servers now use suexec which runs cgi scripts under your user-id. There is no longer a need to set permissions to 777. This will allow any user on the server to be able to edit the files which is a large security risk. Instead of 777 755 should be used.