Once you selected the image you want to add to your page or post, you’ll see a checkbox next to the thumbnail confirming your selection, and see information about it displayed in the Attachment Details pane in the right sidebar of the media uploader.
Attachment Details for your Image
The Attachment Details shows a small un-cropped thumbnail of the image, and important information like the filename, date uploaded, and image dimensions in pixels.
There is a link so you can edit the image, which takes you to the Edit Image page, or you can delete the image by clicking the Delete Permanently link.
You can also edit the following information about your image:
Title: The title of this media.
Caption: The caption for this image. The text you enter here will be displayed below the image.
Alternate Text: Enter the Alt text for the image, e.g. “The Mona Lisa” to describe the media. This alternate text is used by screen readers.
Description: A description of this image.
For more information on these media settings, see the Codex Edit Media page.
Attachment Display Settings for your Image
The Attachment Display Settings (below the Attachment Details) controls how your image is displayed when seen on your site.
You can set the alignment (left, center, right or none) and what size image you would like to display on your page.
Left Alignment aligns the image on the left hand margin, and any text that is on the page wraps around the image to the space on the right.
Right Alignment aligns the image on the right hand margin, and any text that is on the page wraps around the image to the available space on the left.
Center Alignment aligns the image to the center of the page, with no text displayed around the image.
None Alignment Setting inserts the image in to the page with no alignment