WordPress Database Analysis

Hi

I was analysing the WordPress database and was trying to “add” posts and categories into the database directly without having to go through the interface (I was doing this because I needed to dump a large number of data in wordpress directly)

Can you please tell me what do these columns do? I havent been able to figure out their functions!.

1. wp_posts table: “post_name” column This seems to be permalinks function in my opinion. But I havent been able to figure out how to create this manually? I mean, what kind of a function does wordpress use to create the “post_name” data?

2. wp_posts table: guid column This seems to be some kind of an identifier for the posts. But I fail to understand its importance because even if i leave this blank, then also the blog seems to work fine.

Thanks for taking the time to answer my questions.