GPS NMEA Library

Thanks for the example and I have found numerous examples online for working with GPS strings but I'm wondering is there a place I can go to learn more about what all that stuff really means? I mean things like this:

for(int x=0; x<100; x++){
						if(gps_buffer[x]=='*'){ 
							checksum_received = strtol(&gps_buffer[x + 1], NULL, 16);//Parsing received checksum...
							break;

I can copy other peoples work from now til doomsday but I really want to know what all this means so I can do more things in the future. I'm sorry to seem so stupid but this is my first go round with anything like this, I'm learning but I really need more.