It's a little more complex for that but for most peoples requirements the speed is the significant difference. .11b=11 Mb, .11a and .11g have a 54 Mb signalling rate. b and g operate in the 2.4 Ghz GSM. a gear using a 5 Ghz carrier. CCK modulation at 11 Mb, and OFDM at both 54 Mb technologies. 3 non overlapping channels for b and g, 8 for .11a, which can be significant when you saturate a WLAN with AP's. .11a is more of a enterprise technology. Pricepoint was just to high for the home consumer and initially the coverage was poor. With the prices so low, at the moment .11g hardware is the easy choice for residential purposes.