What's the Difference Between Fartlek, Tempo, and Interval Runs? // I never understood these different forms of speed training! This article puts definitions into easy-to-understand language for beginner runners (or those who don't speak running lingo).
Hills are all a matter of perspective. In life, down hills are times when things get tough and you look forward to when you hit an up hill. In running, the down hills are when you can recover and gain power for the up hill to come.