When you upload photos to a page, all the photos can be found here
in the All Photos section. You can also upload photos here first then
select them to add them to a page.
Selecting Photos
Below each thumbnail there is a checkbox icon. Check that checkbox
to select the photo. When you do, you will see a tray open at the
bottom of the screen. That tray has options for creating a new page then
add the photos to that page, deleting, add tags, etc...
To select multiple photos in a row, click the first checkbox, hold
down your shift key on your keyboard, then select the last photo you
want to select.
Tags
Adding tags to photos helps you find photos.
Recent Upload Sessions
Whenever you upload photos either from this section or to a page,
it creates an upload session. By clicking the upload session, you will
see all photos uploaded at that time. You have the option to select all
when viewing an upload session.
Photo Titles, captions and tags
When clicking on a thumbnail you will be able to view the photo
larger and add a title, caption and tags. If you already have a title
& caption in the photo IPTC data, it sytist will try to import those
when the photo is uploaded.
Default sort of the All Photos section
You can change the default sorting view in the Settings -> Photo Sizes & Defaults section.