Marathons are long-distance running races of over 26 miles and are great exercise!
Wow! thats cool! Ive been actually training for a marathon recently, DO you know if a marathon is on a flat road or are there any hills? 
I think they are generally flat, but the event was made to commemorate the run of Pheidippides, a Greek soldier who relayed the victory of the Battle of Marathon to Athens.
Oh ok, I just hope it wont be too hard, I can only run so much up a hill lol. What kinda age limit is there for a marathon i any? 
There aren't any age limits. In fact of the more than 800 marathons held in the world each year, the majority of competitors are recreational athletes.
Wow over 800!!? thats wild. Do you know what the world record is for running in a marathon? Im sure people have broken that 26 mile limit. 
I'm not sure what the world record is but the marathon was one of the original modern Olympic events which dates back to 1896.