Sometimes just beating the bad guys is not enough.
Alternate objectives are goals beyond just killing everyone that you can include in your combats. These encounters still feature enemies to fight, but they also include tasks for the heroes to complete. These could be anything from rescuing hostages, to destroying an evil relic, to holding a scrap of land long enough for reinforcements to arrive.
The book Alternate Objectives includes advice for creating your own encounters with seven categories of goals, plus general advice like using ability checks and making combat optional.
It also includes six sample encounters that you can drop into your campaign, each with multiple story hooks.