A road shoe is most commonly found with a three hole cleat pattern on the sole. This set-up is suitable for Look style and Shimano SPD SL pedal systems. The cleat is exposed on a flat sole platform and is not suited for walking.
A high quality shoe will have a stiff sole enabling good power transfer. Some road shoes are built around a carbon fibre sole, that is not only stiff but also very light. The fastening system for the shoe is often an adjustable Velcro strap, ratchet, dial or combination of each. This allows for a varied and comfortable fit.
The upper material for the shoes varies from brand to brand and even model. A leather upper would be more substantial but heavier whereas an artificial, vented fabric offers a lighter option but with less efficiency in keeping out the elements.
Fit is subjective but ideally the shoe should be snug without restricting movement.
When purchasing a road shoe there are few things to consider:
1. Your current pedals (whether three or two hole cleats SPD or Look/SPD SL style).
2. Intended use. A shoe for commuting would ideally be more robust and better suited to wetter weather, whereas a racing shoe would be light and stiff with an easily adjustable fastening system.
3. Parts availability. A Velcro strap system is unlikely to require replacing but a ratchet and buckle or dial system may wear and need replacing.
4. Fit. A good fitting road shoe should feel snug but not restrictive. In the first instance always order your regular shoe size unless you have previous experience of a particular brand/model sizing irregularities.