Im a new xterra owner from the flat state of Ohio and havent had much experience with my 4 wheel drive yet...I have had automatic transmission most of my life and am pretty clueless on any type of manual or 4 wheel drive transmission....(so please dont laugh if this is a dumb question).

The shifter is labled with 4 positions....2H,4H,N,4L It seems to me that there should be three or four positions but it only feels as if there are 2 when shifting. The first usually in 2H and the second, Im guessing in 4L. It doesnt seem to lock into place in 4H, and I cant tell if its in 4H or 4L....It just seems like there are only 2 gears, 2WD or 4WD. Does the 4 wheel drive decipher H or L when its needed or am I retarded?......Its just sort of bothering me because Im afraid I might tear somehing up.....Can anyone give me a suggestion or explain to me how this works?