what is SQL, i'm new to this in a way

Structured Query Language. It's a syntax to query databases.

whats the difference in running eblah's sql vs their regular forum?

SQL version requires a database. So you'll have to set up and run a database server. I'm not sure what databases are supportet at this time, I think it's only MySQL.
The regular version is file based so you do not need anything else to run it.

oh ok thanks

SQL: Structured Query Language
In effect, you can retrieve data from a database using simple calls:
SELECT <fields> FROM <table> WHERE <condition is true>;
DELETE FROM <table> WHERE <condition is true>;
(the WHERE... is not mandatory)

Not only is it a little more secure and easier to pull and edit information, but it also has a performance increase.  Repeated searches can lay in a buffer in memory, which leads to fast retrievals.  It's necessary for common searches and routines.

Therefore, using something like a forum, where we're getting a post trail for a thread, we might do something like:
SELECT postID FROM post_thread_bridge WHERE threadID = 2;

So this will return all the posts from the table for the second thread in the forum.  Then you can join that with another table to get the post information, or maybe another table that has the user information.  The sky's the limit.

Why change to SQL?
Let's let them develop more features in the original way ( CSS I think it is )