Here's some explanations USOF Standard A-meet Entry Form is available as an Adobe PDF file. This file is viewable and printable with the free Adobe Acrobat Reader version 3.0. The number denotes age on Dec 31 of the year of the event.
Check meet announcement for recreational and non-standard courses.
In the US the courses are named by color. It is very challenging, sometimes as long as Green, but still with safe navigational features. Stay with the Orange course until you know all the advanced techhniques, and regularly come in near the top 3. The navigational techniques required are quite complex and you should be able to really 'read the map' at a detailed level and have all the O techniques mastered. We urge you to respect this for your own safety and enjoyment, and in consideration for the organisers.