The context menu on the Articles navigator (right-click on an article, displayed in the list) provides following functionalities:

Open for editing

Opens all selected articles in separate content tabs.

Articles are opened potentially for editing. Which element (if any) is automatically open for editing, depends on scripting. Normally, a user can select the open a body element when opening an article (Edit > Preferences > Extra > Reopen body). Article is however not checked-out automatically. You can initiate editing by opening any element in source pane, or editing directly in the WYSIWYG pane. Note: you'll be able to edit only if the element is already not in editing elsewhere: in your Fred4, or in someone else's Ted4 or Fred4.

Add Tiled Vertically

If there's already an open article, the selected articles are all tiled vertically with existing one.

Add Tiled Horizontally

If there's already an open article, the selected articles are all tiled horizontally with existing one.

Open for viewing

Opens all selected articles in separate content tabs. Articles are opened for viewing, and you won't be able to initiate editing, but other user will be able (the first one which attempts to open them for editing).

Spike

Spike all selected articles (if possible). Note: you cannot spike articles that are published on any publishing destination, or in a list of any destination of Publishing main tab, or linked to a page. To spike such articles, unpublish them from all destinations, remove them from all the lists in the Publishing main tab, and unlink them from a page.