"Tempo pace" is 85-90% of your maximum heart rate, or fast enough to make conversation impossible but you'll still be able to speak a short phrase. It's uncomfortable but not painful; 30-40 seconds slower than your best 5k pace.
Tempo runs are great for improving speed in longer runs (5k and up) and are usually run in intervals of 2-4 miles, depending on your goals.
Do: 2 miles in BEST mm:ss
