Fetch Plain. what it is?

hi all . While i read from

http://www.slideshare.net/pinaki.poddar/jest-rest-on-openjpa
<http://www.slideshare.net/pinaki.poddar/jest-rest-on-openjpa>

i have view that OPENJPA has Fetch Plain .
What it is please ?
i not know about it .

tank you .
Mauro