An ND filter can be applied to your lens as an attachment. The purpose is to control the amount of light reaching the camera sensor so that slow shutter speeds can be used....adding smoothness to moving objects, such as a stream or waterfall.
The Olympus Live ND mode replicates that effect in the camera by taking multiple images at different exposures and combining them in the camera into a single image. The degree of ND can be selected in the menus, from ND2 to ND32.
The Heron was a perfect subject, because he was completely still....I snapped a few standard images, and then, noting how nicely he was standing still, I decided to try the Live ND feature.
I'm pleased with the result...and was able to hand hold this shot, even though using my Zuiko 300mm lens. Olympus has amazing in-body image stabilization which works with the lens stabilization to give up to 7.5 stops of image stabilization!
Here's the base image (without the Live ND activated) and the Live ND version (PS levels, saturation, and sharpening) with EXIF data for both.