What is execvps?

[Melih Onvural <melih bellsouth net>]

I installed ddclient to handle my changing IP address. I followed the
instructions given in the README file, but when I try to run the script to
start it, it fails and gives me the error message:

Permission denied: execvps

What is this and how can I make it such that my script works?

Thanks,
melih