All due respect, but I don't quite agree with wellnow's terminology and descriptions. In particular, I think his description of anaerobic capacity sounds more like a description of speed or speed endurance.
In my understanding, these are the main training types important to an 800m runner (with sample workouts for an 800 runner):
1. Aerobic endurance
The ability to sustain a moderate pace for a long time without starting to accumulate lactic acid.
This is especially important to 1500m-marathon runners.
Example workouts: LT-pace distance running, easy running
2. Aerobic capacity
The ability to sustain a high output from the aerobic energy system at a pace high enough that lactate would inevitably accumulate if running continuously at this pace.
This is especially important for 800m-5000m runners.
Example workouts: 2*10*200m with 30s rest, 2*20*30s_run/15s_ rest
3. Anaerobic endurance
The ability to buffer lactic acid, transporting it from the muscles to the bloodstream and eliminating it, thus being able to tolerate a higher sustained pace without blood lactate getting too high.
This is especially important to 800m-1500m runners.
Example workouts: 10*200m with 1 min rest, 7*400 with 1 min rest
4. Anaerobic capacity
The ability to tolerate a highly acidic muscle environment and thus sustain a very high speed even when the running intensity is high enough that there's not enough time to offset the lactic acid to the bloodstream.
This is especially important to 400m-800m runners.
Example workouts: 5x200 with 4 min rest, 6x150 with 3 min rest, 600+400+200 with 10 min rest
5. Speed endurance
The ability to maintain very nearly maximal speed even when atp and cp stores have run out.
This is especially important to 200m-400m sprinters.
Example workout: 8x80m with 6 min rest, 4*120m with 5 min rest
6. Speed
The ability to achieve a high maximal speed.
This is especially important to 60m-400m sprinters.
Example workout: 5x60m with full recovery, 5xflying 30m with full recovery
Hope this helps,
/Khell