You probably do not need to use them.

I use them so rarely that I forget. One is federal only and one is state only (probably S)

LOL - Susan... I swear "twins" we are. 😉 

I've used it occasionally, but it never seems to work just right

N= non-source

S= Source & tag to the appropriate state

@mstsax   type it into the search box (within Lacerte) and there should be a help article.

https://accountants.intuit.com/support/en-us/help-article/state-taxes/understanding-source-column-pr...