Photoshop : Difference when drag an image to psd file directly and copy/paste manual

I have an image and I want to move this image to my psd file. I have two ways to do this.

1. 
   

   this is my first solution I often do from very first time I use photoshop. I drag image file directly into my psd file. I often see that this image will be resize base on my psd file if this image is too large and at the corner of layer there is a little symbol.

   
   


2. 
   

   this solution I studied when I watch video tutorial. That I will open this image by Photoshop. Then [Select]\[All] then [Edit]\[Copy] then going to my psd file, [Edit][Paste]. In this case, I see that my image doesn't resize, and doesn't have little symbol at the corner of layer.

   
   

So. are there any differences on two above solutions ? Thanks :)