What do you plan on doing with that "pine tree" in your example?
That would likely prompt me to do things differently, depending on use.
Let's say that you want to use that pine tree in another Image, say in from of a photograph of a lake and mountains. In that case, I would use the Lasso, to Select the pine tree, but leaving extra pixels, which will be addressed later. Then, I would likely Copy that pine tree, and Paste it into the lake & mountain Image. Of course we have those extra pixels, but it's easy to handle them, with but a bit of "painting." Now, with Selection, choose Load Selection and choose Layer 1 Transparency (if the pine tree is on Layer 1), then Save Selection>Layer 1 Layer Mask. Those extra pixels are still there, but we will now fix that. Make your new Layer 1 Layer Mask (just the Mask) active (check that in the Channels Palette, to be certain), and you will see that your Colors are now black and white. With the Brush Tool, paint IN the Mask with Black, and paint OUT the Mask with white. The X Key toggles the Colors, and hence whether you are painting IN, or Painting OUT that Layer Mask.
I like to start with a larger, harder-edged Brush, for a quick "cleanup," but then Magnify to the fine detail in the pine tree, choose a smaller Brush, and perhaps with more softness. I also have a bunch of rather "chisel-shaped" Brushes, for working around leaves, and needles on trees, and shrubs. Do not worry if you Mask too many pixels, as you can hit X and paint OUT the Mask, to reveal them. They are all still there, so you really cannot go wrong, and can always come back, and either hide more of them, or reveal more of them, as you are ONLY painting on the Layer Mask. Be sure to do a Save_As for the PSD, and do NOT Flatten, as you want all Layers, and all Layer Masks, should you change your mind, or revisit that Image.
I thought this could be complicated....and as soon as you said layers, I got lost....I did make a copy of this to notebook and and I will try to make it work...I was kind of hoping for a video, I am visual learner rather reading...I can read but I learn better by watching. As I said I have the documentation and I will go step by step...who knows I might learn layers, which I have avoided all these years I have been messing with PS since ps 2 but never got into layers that much
Chris Cox posted a Google Search URL (if I read it correctly), on Layers and Layer Masks.
I am almost the opposite, in that I read, and learn best. My wife is more "visual," and one would think that it would be reverse, as I am a "visual communicator," and she is a "Regional President" for a major healthcare corporation in the US. Still, I read, and read, and she wants to see it happen. The third type of learning, is by doing. That is # 2 for me, and also for her. Reading of how something is done, is last on her list.
I know that there have to be 100's of video tutorials on Layers (especially as there are so very many aspects to them), but I do not have any bookmarked.
Now, the "Layers Short Course" goes like this.
Once, there were no digital Images. Everything was analog. If one had a photograph, and wanted to change that, their choices were limited. One could add dyes to the photograph, perhaps bleach parts of it, or airbrush onto it. However, one method of airbrushing was to place a sheet of clear acetate over the photograph, and register it (most used metal pins attached to the photograph, and exactly formed holes in the acetate, to make accomplish that registration. The airbrush work was then done to the clear acetate. That was, what we now call a Layer in digital. Where it was clear, we saw the photograph below, but where we added the pigment from the airbrush, we saw that. Then, to get it all together, one put the photograph, plus all registered acetates into a process camera, and shot an 8 x 10 negative, or transparency.
Layers in Photoshop are clear acetate sheets, that are registered with each other, and with the Background Layer. In the case that I suggested, we have another element - the Layer Mask. Imagine another Layer, that is infinitely flexible, that "holds back," or "reveals" parts of that airbrush work. In our case, the "air brush" is the pine tree, but with a bit of extra pigment (pixels to us, in the digital world). We can easily alter that extra Layer - the Layer Mask. We can make the edges sharp, or as soft as you can imagine. [That was always the "holy grail" with regard to analog image compositing. Only the spray of the airbrush could get there, achieve that, and when compositing transparencies, it could not be done. After decades of trying to achieve "soft-edged" lith masks in transparency compositing, when I saw my first Scitex demo, I knew that I was looking at the future.]
Layers are acetate sheets, atop your Background Layer, but with digital, there are really no limits.
The more that you can learn about Layers, and also their Masks, the better off you will be. I consider Layers (and their various elements, like Blending Modes, Layer Masks, etc.) to be the ultimate addition to Photoshop. Think that was with version 4 (not CS 4). When I got my upgrade, I knew that I had "died, and gone to heaven."
Good luck, and do check out Chris Cox's URL. Bound to be many hours of tutorials.
Capt, (do we need to salute?) you sure like to jump in at the deep end. I can't think of too many things more difficult to select that a single pine tree in a forrest of pine trees, but Bill has made a very relevant point 'what will you bbe doing with the selection?' If you are going to composite it into another foreest of pine trees, then I think you can see how that would make things easier. Even if you wanted to composite it onto a contrasting background, it would be an easier job than you might think, because there is absolutely no need to be accurate - any overspill of the selection into a neighbouring tree would look like part of the first tree, so no problem.
I noticed you asking about Layer basics, so this might be a step too far, but this alternative take on Refine edge by Martin Evening would be the perfect apporach to the Pine Tree problem: