Photoshop Layers?

I'm just new to photoshop and was wondering about layers. what do they do? Because what i want to do is, i have a couple of pictures and i want to put them all in one background. so how do i do that? for example like these pictures

http://i246.photobucket.com/albums/gg82/...

http://i99.photobucket.com/albums/l310/v...

http://i246.photobucket.com/albums/gg82/...

or make opposing people go against eachother like

http://www.flickr.com/photos/7247517@N02...

http://i246.photobucket.com/albums/gg82/...

so how do you make pictures go on top of eachother on one...thingy. thanx!

Photoshop Layers?spyware remove

open the images you want to join. then you can click and drag layers from one photo to the other. because they are in separate layers, anything you do will only affect the layer currently selected. using the move tool, you can move the different images around to where you want them. and as iron chef tome said, you can erase the edges of a photo to make it look better. Also you could use a layer mask and adjust the opacity to blend them together. I could explain it but i dont feel like it now. when ur done u can merge the layers into one.

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none of your pics are working..
Like what Lilly said, go to www.univision.com and it should help with the photoshop layers.
I don't have photoshop but I have Gimp which is similar. When I use layers, I use them for color selection. Say you have a photo that you want all black and white except for one object that you want to remain in color. What you do is copy your photo, open it as a new layer, change the new layer to black and white then paste the black and white copy over the color photo. You will have to anchor it to the color photo so it won't move when you start "erasing" the black and white to show the color under it.