The Healing Brush Tool is used to remove small areas such as skin blemishes. It does this by you selecting an area of texture that you want to copy, using ALT + CLICK, and then painting on the area to change. So be careful to sample from an area which matches. The colour of the existing area remains intact. This is good for blending texture and colour together.
It is best used on a blank layer above the layer to edit, with the Sample box set to Current and Below, which give non destructive edits.
The Healing Brush Tool is different from the Healing Brush and the Clone Stamp in that it only paints texture into the new area under your control. The Spot Healing Brush does the same thing but Photoshop guesses the texture to use, and the Clone Stamp paints both texture and colour and you have to do the blending by careful painting.
When editing skin to remove blemishes use a harder brush to ensure the texture is copied across. Removing darker areas using Lighten Blending Mode helps, as does removing lighter areas using Darken Blending Mode.
