Why we use check_dummyse in nagios?

Hi,

Why we use check_dummy in nagios? I have this following entry in services.cfg.

check_command check_dummy!0

and I get alerts

[05-06-2010 16:49:59] SERVICE ALERT: W2;str;UNKNOWN;HARD;1;check_dummy: Could not parse arguments
[05-06-2010 16:48:59] SERVICE ALERT: W2;str;UNKNOWN;HARD;1;check_dummy: Could not parse arguments
[05-06-2010 16:47:59] SERVICE ALERT: W2;str;UNKNOWN;HARD;1;check_dummy: Could not parse arguments
[05-06-2010 16:46:59] SERVICE ALERT: W2;str;UNKNOWN;HARD;1;check_dummy: Could not parse arguments

Any reply will be highly appreciated.

Many thanks.

Sam