input plane vs. view window

[Dean]

Hello all,

I remember seeing a good explanation somewhere between modeling on the  
input plane vs. sending mouse input to the orientation of the view  
window. CAn somebody point me to it, i'm driving myself crazy with  
knowing or more accurately NOt knowing where my model points are  
landing on an object or the space within which it is being modeled.

thanks in advance for helpful direction

Dean