building custom scripts.....

hi everyone…somebody plz help me…how can i build custom scripts…plz give me a small code…like…

@load … <------- // I dont know why this is used for…
@prefix … <------ // same problem with this…

and do we need to save it as xxx.bro and store in SITE directory and can we access it as

#bro -r trace.out xxx.bro

plz tell me the procedure so that i can get the start…

Thanks & Regards
Navdeep Singh
094640-77449