Actually that isn't what a kernel is...
BIOS -
BIOS - Wikipedia, the free encyclopedia
KERNEL -
http://en.wikipedia.org/wiki/Kernel_(computing)
How to find these thing's out without asking a question... GOOGLE -
Google ( or whatever search engine you may like )
Okay...now that wikipedia has been used for a general definition...here are a couple of points YOU need to know.
- You need to be rooted to change from the default kernel.
- LV means Low Voltage (some phones CANNOT run these and you'll know that if you get caught in a "boot loop" after installing it). IV means intermediate voltage, and HV means high voltage. Always start installing new kernels with the lowest voltage option as lower voltages = lower temperatures.
- Do not just jump to a 1.2 or 1.3GHz kernel. Some phones are unstable above 1.0GHz but I've gathered that MOST people can run at least 1.0GHz without problems. Some people don't go above 800MHz cause they say the speed difference isn't noticeable above that...I disagree but my experiences ON MY PHONE are that 1.0 or 1.2 are indeed faster than 800MHz

Try 800MHz or 1.0GHz kernel and then step up from there to see where your phone will perform best. You may have one of the phones that can go to 1.3GHz...mine can't so 1.2 is my max and depending on the kernel, 1.0 or 1.1GHz run better.
- Slots...these are the number of "steps" that a kernel has for overclocking. You use these slots with SetCPU to set up various profiles to maintain low temps when charging, extend the life of your battery (you don't want your phone to run at 1.0 GHz when it's sleeping...it is wasting battery just performing background tasks), etc.
5 and 7 slot kernels are the most common nowadays.
Example: A 7 slot, 1GHz kernel might have the following "steps":
1.0GHz, 900MHz, 800MHz, 700MHz, 600MHz, 500MHz, 250MHz
While your default profile in SetCPU might have a Max speed of 1.0 GHz and a minium of 250MHz, you can set different profiles to use these slots as mentioned above. You could have a profile for when you are below 25% battery where the phone's max goes down to 700MHz because you are going to become battery conscious if you get low on juice...does that make sense?
- Some ROMs only work (or work well) with certain kernels...check the Dev's release notes to see if there are recommended kernels to use for their ROM.
I don't know what you do or don't know about overclocking but I thought I would provide a little "Droid specific" kernel information.