Why does the edit tool remove multiple layers at a time?

[LukeReed]

I have created a layer from an existing layer using the select by location tool. I then saved this layer and removed my main layer from the map. I had to trim up the new layer to fit my project. When I add back in the original layer to overlay the new layer and show the changes the original layer has been deleted in the same places as the new separate layer. I have tried this process several times and always get the same result of the original layer being deleted in the same places as the newly created layer.

Any ideas?

[RichardFairhurst]

Creating a new layer in ArcMap by using copy/paste, saving a layer file or creating a selection layer only creates a new view of the original data, not a new copy of the original data.  This is useful for changing symbology, labeling and other presentation properties of the copied layer within a map of a single data source.  It is not useful for duplicating a data source so that the original data source is untouched by editing.

To create a copy of the original data source you need to export the layer (right-click the layer->Data->Export), copy/paste the feature class in ArcCatalog, or use a geoprocessing tool that copies a feature class like the Feature Class to Feature Class tool.

[LukeReed]

Thank you very much Richard. I was getting frustrated. This makes sense now.