Using the Eraser Tool
When you use the Eraser tool to erase on a raster layer, all pixels
in the tool’s path become transparent. When you erase on the background
(which does not support transparency), the Eraser tool acts like a paintbrush;
all pixels in the tool’s path become the current foreground (left-clicking)
or background color or material (right-clicking).
To use the Eraser tool:
On the Tool palette, choose
the Eraser tool 
. (It's grouped
with the Background Eraser tool.)
On the Tool Options palette,
choose the brush tip, size, opacity, and other options. See Setting
Brush and Paint Options. For the opacity setting, 100% erases pixels
to complete transparency and a lower opacity erases pixels to partial
transparency.
Drag in the image to erase as
follows:
To erase pixels,
drag with the left mouse button.
To restore erased
pixels, drag with the right mouse button.
To erase a straight
line, click once at the beginning point, then press Shift
and click the end point. To continue the straight line, move to the next
point and press Shift and click.
Note: If you erase on
the background, the eraser strokes change to the background color when
you use the left mouse button or to the foreground color when you use
the right mouse button.
Cloning Parts
of Images
Creating Brush
Tips
Erasing
Painting
with the Paint Brush or Airbrush
Replacing Colors
Setting
Brush and Paint Options
Using Brush Tips