Multi-DB help

Hi There

I am a newbie to the wordpress MU so please excuse me if I ask questions that seem simple.

I just did a fresh install of MU , but now want to enable the MultiDB plugin. I had a look at dp-config-sample-256 that I downloaded with the plugin.

What is a global table?
Code: add_global_table('some_global_table');

I have wordpress Mu installed on a dedicated server with mysql server also on the same server ,

Code: add_db_server(DS, DC, READ, WRITE, HOST, LAN_HOST, NAME, USER, PASS)

In the above code will DS = localhost because I am running mysql on the same server?
What Does Read and Write Mean
Would host be the ip address of my server?
What does Lan_Host Mean?

Code Example: add_vip_blog(1, 'vip1');
Also what is VIP Blogs?

Thanks and all help will be appreciated.