⭐ The council on this thread most worth remembering, and most often misremembered — it condemned Semi-Pelagianism, but did not adopt predestination.
The issue
Who takes the first step toward salvation (initium fidei)?
Claim
Augustine's side: even the beginning of faith is given by grace. A person cannot take the first step by himself.
Counterclaim
The Semi-Pelagian side (Faustus of Riez put it most plainly): the beginning of faith is an act on the human side, not something grace enables a person to do.
The ruling
⭐ The council condemned the main points of Semi-Pelagianism — confirming that the initium fidei, too, comes from grace. ⚠ But the council gave no approval at all to predestination. Olson records the outcome: both the most fervent supporters of Augustine and his strongest opponents lost.
What was at stake for salvation
⭐ Note that the two sides' concerns for salvation here are not symmetrical: Augustine's side was guarding the principle that grace must be wholly undeserved — otherwise salvation would include human merit; the Semi-Pelagian side was guarding the principle that a person must truly be responding — otherwise repentance and faith become a piece of theater. Orange's verdict was in effect a compromise between the two — and the compromise could stand because what the two sides were fighting over was never whether a person must respond, but who starts that response.
Aftermath
⭐⭐ What this council settled was the shape of the Western church's official position for the next thousand years: grace goes first, but is not irresistible; a person cannot take the first step alone, but neither has he been predestined. ⚠ A common mistake is to treat Orange as the total victory of Augustinianism — it was not. What it adopted was an Augustine with predestination cut away, and this matches exactly the Augustine shaped by the anthologies of Prosper of Aquitaine. ⭐ A thousand years later the Reformers read Augustine's complete works and rediscovered predestination; this is why the shock was so great — the Middle Ages read the anthologies, the Reformers read the complete works.