How to use Head Code in 3.1

Head code has been introduced in 3.1, but I don't really understand what it is or how to use it. Could anyone give me any tips please?

I know from other threads, the importance of title tags and meta description, but meta tags are now irrelevant as far as Google is concerned (why is this feature in 3.1 as they're redundant now?) but I don't know how head code fits into this mix.

Hi Jens, thanks for that.

I don't really understand that to be honest, but let me just you ask this, does head code have anything to do with search engine rankings or indexing or anything to do with search engines at all?

thanks

Cheers, Alexander.