Hi Ting Ting
It just means, doing NoS without making any additional restrictions or extra rules or modifications.
Plain NoS, with nothing extra added.
"Vanilla" just represents "Plain"...
So many people often try to change NoS to make it more "Diet like" but it's enough of a challenge to do the plain version..
Why would anyone want to make it more complicated by adding rules?
Hope you understand it better now.
![Cool 8)](./images/smilies/icon_cool.gif)
Debs
ps.. "Tweak" is a slang phrase which means a little change/modification you make to something, to make it more personalised.
In this case, when people do "tweaks" to NoS, it's to make it a bit more personalised in hopes it will be more successful or livable for them.