welcome to gimp-forum.net
A selection is image wide but you do have to select the appropriate layer when applying. Copy in one active layer / Apply in a different active layer
With copy/ paste there are various options If you just paste (on a new layer) it will be in the same place and all you need to do is anchor the floating selection. Layer -> Anchor Layer Note there is lots you can do with the temp floating layer - scale / rotate / move for example.
Paste-as-a-new layer results in a layer just the size of the selection with origin 0,0 (top left corner)
However, from the rest of your post.
When you say no background, do you mean a solid colour background rather than a transparent background. That would require no editing. screenshot: https://i.imgur.com/n4M1wQt.jpg
If you have a solid colour background there are several ways, some better than others, to remove it. All depends on the image.
Something simple like this:
1. Give the layer an alpha channel if it is not there: Layer -> Transparency -> Add Alpha Channel
2. Try the fuzzy select tool and select the background. https://i.imgur.com/XCCtGUj.jpg
3. That often gives a faint border due to anti-aliasing so grow the selection by a pixel (or 2) Select -> Grow
4. Now you can remove the background Edit -> Cut then kill the selection Select -> None
https://i.imgur.com/WxvmaXG.jpg
Remember to Save your image as a Gimp .xcf - which keeps all the layers etc. When complete you can Export as a png / tiff / jpg
A selection is image wide but you do have to select the appropriate layer when applying. Copy in one active layer / Apply in a different active layer
With copy/ paste there are various options If you just paste (on a new layer) it will be in the same place and all you need to do is anchor the floating selection. Layer -> Anchor Layer Note there is lots you can do with the temp floating layer - scale / rotate / move for example.
Paste-as-a-new layer results in a layer just the size of the selection with origin 0,0 (top left corner)
However, from the rest of your post.
When you say no background, do you mean a solid colour background rather than a transparent background. That would require no editing. screenshot: https://i.imgur.com/n4M1wQt.jpg
If you have a solid colour background there are several ways, some better than others, to remove it. All depends on the image.
Something simple like this:
1. Give the layer an alpha channel if it is not there: Layer -> Transparency -> Add Alpha Channel
2. Try the fuzzy select tool and select the background. https://i.imgur.com/XCCtGUj.jpg
3. That often gives a faint border due to anti-aliasing so grow the selection by a pixel (or 2) Select -> Grow
4. Now you can remove the background Edit -> Cut then kill the selection Select -> None
https://i.imgur.com/WxvmaXG.jpg
Remember to Save your image as a Gimp .xcf - which keeps all the layers etc. When complete you can Export as a png / tiff / jpg