The Directional Light is a simple light source that illuminates from a infinite location (figure 1). Therefore, only changes in angle will affect the direction of the illumination, it does not matter where the light source is placed in a scene.
Figure 1: A Directional light illuminating the scene
On/Off - Turns the light on or off in the scene.
Target Mode - Toggles the target direction on or off for the light.
Target Distance - Determines the distance the target is from the light source.
Emission - Allows for a Texture or Black BodyAn opaque object that emits thermal radiation. In Octane, this is used to designate illumination properties for mesh emitters. emission node to be connected here for additional control over the illumination.
Light Sampling Spread Angle - The larger this value, the softer the light source's illumination.
Use in Post Volume - Enables or disables the light in post volume rendering.