The History brush in Photoshop is used for fixing blemishes and errors created in the retouching process, but it can also be used to create new effects. We show you how in our Adobe Photoshop courses. 
Say you’re halfway through editing an image. Now open the History panel: Window > History. This shows you a list of all the steps so far performed in creating the image, the bottom state being the most recent. You can of course go to previous states by simply clicking further up the list. And also click downwards to redo the changes. Note also the Snapshot icon on the bottom of the History panel – hit this periodically to add a new snapshot – this allows you to review “milestones” on your editing journey.
Note also the small square to the left of each history state – clicking on this sets the Source for the History Brush. For example, if you have done a lot of work on an image, but realize that you’ve made an error a while back in a certain area. Select a history source from a previous state when this area looked ok. Now select the History Brush and paint back int his area – it returns only that area to its original condition.
Another use is in applying effects to selected areas of an image. For example, add a filter from one of Photoshop’s 100 filters. Then select that state as the History Brush source. Now select the state prior to this one as the one to work over – paint in certain areas with the History Brush to apply the effect only to this area.
Many more tips and techniques can be found at the Adobe website. And see many examples of our clients’ work on our Facebook page.
Other related Photoshop Blog Posts:

• Photoshop interface
  
• Photoshop for fashion
• Photoshop deep etching
• Photoshop animated gif
• Photoshop actions