There are the following:
802.11a, 802.11b, 802.11g, 802.11n
I've never had or seen an 802.11a to be honest.
When I started using wifi routers, b was the standard (11mb/s data transfer speed). when g came in it 54mb/s. n is the current standard which is double g (at least 108 mb/s) but I believe you can much greater than that.
I still haven't got to n yet, still on g. To put it into perspctive, I have a reasonably fast broadband at 30mb/s and my wifi is 54mb/s.
To be able to transfer at the optimum rates for b, g or n, both the router and the wirreless card (be that in a phone, PC, whatever) must both have the ability to connect as that standard.
If by Kernel, you are refering to the Android kernel, the kernel may need to have capabilities of connecting your phone to your wireless router in Wireless N mode (even if your phone only has a wireless g card) so you dont have to change your n router to g just so your phone can connect