The eraser tool in photoshop is a very common tool and will also use it a lot in photo restoration. The eraser tool basically removes any thing that is one the current layer when you click on it. the eraser can be changed in size and also changed in hardness. the hardness of the tool will determine how much the edges of the selected area is blended into the non selected area. For photo restoration i use this tool most often when quickly removing a background that is to be replace and also on more details work when you need to be careful around a ceertain area that is having it's background removed. One tip i would give when doing photo restoration or any other kind of work with the eraser in photoshop would be not to drag too much too much as if you make a mistake and would to undo your work, it will undo everything from the point you first clicked the mouse. therefore, it is better in general to do lots of clicks rather than one long drag as if you do make a mistake you wont have to go back and do loads of work you have just done.