Benefits
Once the PCs meet all the requirements for an improvement, the steading gains the listed benefit(s).
Many improvements include a benefit of "increase Fortunes by 1." This is a one-time gain; when Seasons Change and Fortunes reset Seasons Change, this benefit no longer matters.
Some improvements provide a passive, ongoing bonus to stats like Prosperity or Defenses.
Other improvements provide new player moves, triggered by a particular action or event. Many such moves are triggered when the Seasons Change (in general, or to a specific season); you might want to note these on the front of the steading playbook, as a reminder.
The benefits for each improvement are mostly mechanical, but don't forget about the fictional impact! If the PCs unlock the Aurochs Hunting improvement by cooperating with the Hillfolk, then they've not only gained a new move and resource, they've improved their relationship with the Hillfolk!