Key takeaway for HDR and lighting: these settings simulate the eye's reaction to lighting. In other words, the level of ambient lighting in a game world is often artificially high in order to provide some baseline of uniform visibility. When HDR is enabled, ambient lighting is really polluting the luminance and tone of the scene, and should be reduced as far as possible or acceptable. As you look towards bright lights (intensity > 1), tone mapping simulates your eye adapting the rest of the scene to appear darker with less detail. Conversely, as you look into dark areas with low ambient light, your eye will adapt to see more detail in the darkness.
HDR: rendering to a framebuffer that allows a higher dynamic range of color and lighting, outside the typical [0, 1] range of a low dynamic range (LDR) renderer.
Tone Mapping: To quote wikipedia, "Tone mapping addresses the problem of strong contrast reduction from the scene radiance to the displayable range while preserving the image details and color appearance important to appreciate the original scene content." It also simulates our eyes adaptation to brightness and darkness. http://en.wikipedia.org/wiki/Tone_mapping
Blue Shift: a tone mapping modifier that shifts the color to simulate the affect of darkness on our eyes rods and cones. Best used at night, or in dark environments like a cave or dungeon.
Glare Type: the type of glare "smear" that is applied to lighting (usually seen as a star pattern)
Key Value: also known as the middle grey value, this is the bottom cutoff for luminance
Adaptation Multiplier: increases or decreases the rate at which the tone mapping and luminance calculation occur
Bloom Scale: effectively, a multiplier of the brightness of the glare
Star Scale: effectively, a multiplier of the size of the glare