chain rings are the sprockets on the front of the drivetrain where your pedals connect to the crankarms then the crank. usually 3 or 2 sprockets on a mt. bike or hybrid.cross country can be any thing from a short gravel road to the Appalachian trail or wide enough for people to pass each other( doubletrack) to skinny, twisty, rooty,rocky,sandy,hilly, muddy,just plain nasty or in good shape but still narrow(singletrack). before a ride check your bike for obvious damage such as cracks in the frame or components,check for splits or fraying of your cables,check your brakes to make sure they are in good shape and adjust as needed, check to see if the gears are shifting ok. check tires for pressure and bubbles in the tread. check rims to make sure they do not look too much like a taco shell. as far as after ride or general maintenence make sure all parts that are supposed to move do so and all parts that should not do not, keep your chain clean after riding, as well as brakes, sprockets,rims( if you have rim brakes). if you ride in bad conditions you will need to lubricate your chain,cables, and bearings that are non sealed. a good LBS(local bike shop) can do a tune up for not a lot of money and the good ones will show you a lot of do it yourself tips to keep your bike in good shape between visits.for cross country riding a triple crown fork should be unneccesary. theres probably things I have left out but many here are very knowledgable and willing to share their expertese. welcome to the forums and happy riding