I have a photo of someone's profile. I have used the Lasso tool to select the sillouhette of this person. I would like to apply a gradient to everything in the photo (the bckgd) leaving the person themselves unaffected by the gradient. I press m after I select the person with the Lasso tool, and now there is a bunch of red in the background showing me that I have somehow isolated the person, But I do not know how to proceed. Thanks!
From your struggle I believe you are new to Photoshop.
There are multiple ways to achieve this, below is a productive way to do it.
You need to use the Layers Palette (if not showing then you can find it under Menu --> Window)
The Layer Palette will allow you to create multiple layers for you to stack under each other.
Now press the new button on the Layer palette to create a new layer, this will create a new layer above the image layer you already have, nothing changes because the new layer is transparent (think about it as a transparent film paper on top of a photo in real life).
You now need to put this layer under the image layer by drag the new layer under the one below, if the layer that has the image is called Background then you wont be able to do, to fix that first double click the word background on the layer and rename it, then you will be able to place the new layer under the background layer.
So now the new layer is in the right position, this layer will be used for the gradient, so create the gradient you need on this layer.
Finally, select the layer with the image you need to crop, take the lasso tool and select the are you need to keep in foreground, once you are happy with the selection, press the Mask button (beside the fx button at the bottom of the layer palette). Now your portrait is masked and the background will show through the new layer below it.
Please let me know if you need further help. Mamoon