…without using a selection tool or erasing anything.
It’s not uncommon to need to remove the white background from an image and make it transparent (key it out in video terms). This can be necessary to make it more presentable on a webpage or presentation. While Google images have a lot of transparent PNG images to offer, the larger and higher quality versions are sometimes white background only.
There are a number of ways of doing things within Photoshop. Accomplishing this is no exception. This is a great alternative to e.g. using the selection tool or magic wand to roughly remove the white and simply rub it out. It creates superb results and I guarantee that you will use this method in future if you haven’t already.