Medieval Torah authors divided all actions into three:
- Chovah. (Obligation.)
- Issur. (Prohibition)
- Reshus. (Neutral.)
Rabbi Chaim Greinemann noted that this division is not accurate. On a superficial level, sure, Halacha keeps most deeds neutral. Nevertheless, once there is no obligation to do something, there is always some alternative, preferable action, occupying the same time and space (e.g., Torah study!).
(I could explain this more effectively if I had the time.)
Maybe-maybe this is is what the Aruch Hashulchan means in his Hilchos Shilu’ach Haken, 292:4:
דכל רשות שבתורה היא כמצוה, רק לגבי חובה רשות קרו לה