hello and welcome to fcc forum 
not sure what seem to be confusing here, but its saying here two ways of “associating label and input”
one of which is as “nesting” i.e. label => input
or other is through reference, using “for and id” , i.e. <label for=‘test’>…<input id =‘test’>
if you need more insight about on this, implementation and as such, feel free to look at my reply at this link as well, happy learning Learn HTML by Building a Cat Photo App - Step 55 - #3 by bappyasif