Photoshop Layers Panel Essentials

Layers Panel and Use masks to hide layers in Photoshop

 Changing The Preview Thumbnail Size

Step-1> Click on small menu icon(right side)

Step-2> Select Panel Options

Step-3> Select as you wish to see the Thumbnail Size

 Result as below Image

Alternate option : - Right Click near Layer Panel and get the option to select the Thumbnails size 

Layer Mask : -

> Layer Mask allows you to control a layer's level of transparency or Opacity.

> It is useful because it will keep your original image as well and cover your original image with     mask.

How to create Layer Mask 

Turning Off Default Layer Masks

Hide(erase) the second Image Background

Use Brush Tool to hide (erase) the second layer

See the Above Panel while you select the Brush Tool

Now Start Erasing the background of second Image

Now you can place the second layer image as per your requirement

If you want to recover or back your original image then Turn-off layer Mask

conclusion:- This is the reason why we use the layer mask rather than the opacity option. we can recover back our original image as well as we can edit/erase the image as per our need.