CheckSphere returns a boolean:

bool found =
    Physics.CheckSphere(
        transform.position,
        2f,
        layerMask
    );

OverlapSphere returns colliders:

Collider[] results =
    Physics.OverlapSphere(
        transform.position,
        5f,
        layerMask
    );

Useful for:

• explosions
• nearby enemies
• interaction zones
• area attacks