LINE OF SITE IS GROUND WAVES
line of site travels from one antenna to another as long as they are in sight of each other
ground waves travel along the ground from one antenna to another as long as they are in 'sight' though lower frequecys tend to be more 'ground' waves because they 'hug' the ground better
(you do realize that just because it says line of site, doesn't really mean that you can see it yourself. i can be 150 miles away from Pittsburgh PA and still pick up 105.9Mhz on my radio and that is called line of site and ground waves, though obviously i cant really see the source antenna)
>>Note that for AM radio stations the ground wave (in light blue above) doesn't go very far. This means numerous stations can be put on the same frequency without interfering with each other — assuming they are far enough apart. (Keep in mind that this drawing can't be anywhere near close to scale and show these things.)
every time i answer your questions i feel like im doing your homework.