suexec is an apache module which allows running apache under the username and usergroup of the file being executed.

example: if a file index.html is owned by user ap1 then when apache uses this file under suexec then apache runs under user ap1 instead of default user apache (or noboday in some cases)...

phpsuexec and suphp are similar approaches... suphp is newer than phpsuexec
suphp is an Apache module that lets PHP scripts run as the owner of the script, instead of the default apache user. This offers many security and usability enhancements to the world of PHP web serving. Mainly, when users create and modify files in their directory with PHP scripts, they don't need to make those files world-writable!