memory portion tied to -g switch of sqlservr

I want to know what this is virtual memory address space is . Where can i
understand more about this particular allocation and why just 256MB is given
for it ?
Just a bit confused
Bunch of good articles here:
http://blogs.msdn.com/slavao/
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
"Hassan" <hassanboy@.hotmail.com> wrote in message news:eW40%23lP4FHA.2640@.TK2MSFTNGP09.phx.gbl...
>I want to know what this is virtual memory address space is . Where can i understand more about
>this particular allocation and why just 256MB is given for it ?
> Just a bit confused
>