I think there\'s a few different categories for you to consider depending on weight, foot type, etc.
Here\'s a little breakdown for your reference...
1.) track spikes: if it\'s a track spike, you\'re looking at a really minimal EVA foam midsole in the forefoot (3-5 mm), with a 5 - 7 spike configuration plastic plate making contact with the ground. If it\'s a distance spike (entry-level), generally there\'s a little more heel foam to handle the impact. Sprint spikes have very little foam, if any in the heel, but the plate is much more rigid to provide more energy return.
2) cross country spikes/flats: generally xc spikes/flats have a complete midsole in the forefoot and heel with a rubber outsole for traction. the spike version has a plastic spider plate sandwiched between the EVA foam and the rubber outsole. This is where you screw in your spikes. XC spikes are usually longer because the spike has to be long enough to extend beyond the luggy outsole and make good ground contact. The flats are usually the same design, but the spider plate is remove (foam replaces the cavity where it was). The design of the outsole replaces the holes where spikes would have been with a rubber \'nipple\' to simulate the shape of a metal spike.
Most spikes have a negative heel draft...meaning that your heel rocks back lower compared to your forefoot. Feels weird when your walking but when you run it\'s an awesome sensation.
3) Racing flats: Generally this term classifies shoes that are between 4-7 ounces. As mentioned before, there\'s a little more foam under the heel, and not as much negative draft (meaning your heel starts to sit level if not higher than your forefoot) A lot of times, you\'ll find that the sole unit is \'road flat\' meaning that there\'s not much arch-scooped out..the whole profile is low to the ground. A lot of elite runner\'s prefer this type of shoe because the weight is super light and the flat road contact handles their footstrikes better. So if a runner is a midfoot striker, when they land there isn\'t a gap in the arch where they might get no cushioning or a \'void\' feeling. some examples of a racing flats would be Nike Mayfly,Brooks T5, Asics Piranha SP, Nike Katana Racer,Mizuno Wave Universe 2,Saucony Type A2
4) Lightweight Trainers: These are usually shoes that range from 8 -11 ozs. They typically have a little more of everything. A little more foam under the heel, but still lower profile. Usually more of a midfoot shank for torsional rigidity, sometimes a medial post for support in case you overpronate. The outsoles usually have a little more durability built into them and are slightly thicker...hence a little more weight. Some examples would be Asics DS Racer, Brooks Racer ST 3, Saucony Fastwitch 3, Saucony Tangent 3, Mizuno Revolver 5
5) trainers...there\'s a whole lot more breakdown here...but i\'ve already written enough.
Personally i love running in super light shoes but I\'m not a light framed guy AND because i run more midfoot/forefoot it makes me really prone to shin splints.
anyway, have fun with your running.