Not trolling, can't figure out..

Hello All,

I am looking to talk with people to help me figure out what sa-exim is  
as opposed to regular exim.

It looks like things you can normally do in exim but sa-exim makes  
them 'easier'? or 'standard'?

I guess I don't understand what sa-exim does as opposed to  
spamd_address (and appropriate rules)

Thanks in advance for any thing that would help