The Image Block
The Image block is the default block used when images are pasted or added from the Media tab the left sidebar.
The Image block has some options that make it useful for some purposes. That said, the UI Image block is often preferred. The UI Image block has more Semantic UI options that make it look better and matches the overall look and feel of the site.
Pasting an Image
Pasting an image will result in an image being uploaded to the Media Center. While in a new paragraph block, right click and select paste or use Ctrl+V. The image will show up as an Image block.
Removing the image from the content does not delete it from the Media Library. Use Paste then use undo (twice) or delete the block to remove the pasted image from the content. The image can then be used anywhere by selecting it from the Media Library as usual.