general portinstall question about port names

[Tabor Kelly]

Hello,

I have a general question about how portinstall decides what port to 
install.

When type "portinstall openoffice", portinstall asks me which of the 4 
openoffice ports I would like to install.

When I type "portinstall gimp", portinstall installs graphics/gimp1. Why 
not graphics/gimp, or ask me like it did for OpenOffice?

Thank You,

Tabor Kelly