Adding images from "Photos": Google Photos, that is

toolbar > Insert image > Photos

The "Photos" option provides direct access to all the photos in Google Photos, for the blogging account you are using.

The Photos option lets you insert images from the linked Photos albums.

That's an important distinction if you have more than one Google account (I have three). You won't see photos that you took or uploaded using another account, even if you share them.

To add images from another account, download them to your device and then insert them using the "upload" option.

You're inserting a copy

When you use "Photos," Blogger makes its own copy of the image you insert. You can view these using the Media Manager.

That copy, not the original Photos file, is the file that Blogger uses. Delete it and you will leave an ugly hole in your blog.

Blogger provides free and unlimited storage of images, though the format makes it essentially impossible to use them outside of Blogger.

Upload • From Blogger

From Photos • By URL • Drag & drop