Questions about Kernels.

I'm pretty new to the world of Android, as far as rooting, modding etc. Previously I had a pretty bad Exhibit II 4g running 2.3.6, with a whopping 512mb of RAM. Recently (read: 3 days ago) I got a Nexus 4, (6-7 weeks shipping time... I was jumping when UPS finally knocked on the door) and I'm loving the thing. It's fast, light, beautiful, and best of all, it's got Jelly Bean; no more gingerbread-era Touchwiz for me.

The one disappointment I have with the device is the battery life. There was a small problem where it would display as fully charged, when the phone has just been plugged in, but a quick reboot took care of that. Having said that, the battery still isn't the greatest in the world, considering it doesn't have LTE. I've recently heard a lot of people talking about installing Franco Kernel, and this massively improving battery life.

Now, again, I'm relatively new to this, but can anyone tell me exactly what Franco Kernel is, why one would install it, and what it would affect? Will it do anything unsavory to my phone, as I'm still relatively hesitant, as far as customization goes.