Flattening puts all the laysers on the lowest layer and removes empty layers., any floating selection will be anchored and moved to the bottom of the layer stack.
Flattening layers just merges all layers down into one. It reduces file size, but once the image is saved and Photoshop is closed, you will no longer be able to undo the change and edit those layers separately.
PHOTOSHOP
Photoshop is picture editor,what you mean?good picture editor?best free picture editors are GIMP and Picasa,i recommend to you Picasa
no
from filter menu
Adobe Photoshop CS5
You can use photoshop or another picture editing program to digitally edit the picture.
One only - however, pre-flattening there could be considerable numbers of layers making up the pictures content
Photoshop can do this
Adobe Photoshop CS5
Open Photoshop, open your picture in Photoshop from File>Open, then start making changes. Of course if you are unfamiliar with Photoshop, you may want to learn the basics first.
photoshop