Most of these items can also be found if you right-click on the page in the content tree.
Duplicate - makes an immediate duplicate of your page and places it directly underneath the original in the content tree.
Copy to - makes a copy of your page and you decide where to copy it to in the content tree.
Move to - moves your page to where you decide. When moving a page, Sitecore will create an automatic external and internal redirect for you. You will see these notices in the yellow block at the top of the page. Don't forget to publish the page again if you've moved it.
Delete - deletes page. If page has internal links to it, Sitecore will ask if you want to relink to another page instead. This way you do not break links. A deleted page is not immediately permanently deleted. You can restore it from the trash bin under /sitecore/shell. The bin does get emptied next day.
Rename - renames the page URL and name in the content tree. Keep in mind that renaming pages will create a new url which can skew Google analytics reporting. Renaming a page will break any external links to this page. If you want to be safe, then create a redirect in the Redirect Module.
Display name - this allows you to create a new URL/name on a different language version of the page. For example, if the original page is in English, named "canal tours", use the display name on the German version to create the URL "Grachtenrundfahrt". This will also rename the page display name in the content tree of that language for easier tree navigation. DO NOT use the display name in the same language as this will create two URLs for the same language. This confuses Google and the visitor.
Sorting - allows you to move the location of the page in the content tree up or down. This won't change the URL. Mostly used for easier content tree navigation.
Links - the list under "Items that refer to the selected item:" tells you all the locations (pages, widgets, etc) that link to this page. You can also use this function on images, might you want to know where an image is used around the site. Bear in mind that this list can contain older versions of pages or widgets, meaning, the links are still there in the CMS but since it's an old version, it is no longer visible on the live site. The list under "Items that the selected item refer to:" tells you what this page links to. The latter is less relevant.
My items - Shows you all the pages you currently have locked (are currently editing / have forgotten to check in). You can unlock all your pages in one go using the Unlock all button. It's handy to occassionally check this list and unlock all your items so others can access them.
Edit - Locks the item so you are the only person working on that item.
Check in - Checks in the item once you're finished editing, so others can access the item.
Approve - Approves the item for publishing. Once approved, the page is also published! You can only approve the page if you have it locked (you will see it greyed out, otherwise).
Globe icon - publishes the page in all languages.
Publish item (dropdown menu) - publishes the page. You will be given the option to publish subitems as well. And to choose in which language you want to publish.
Experience Editor - opens the page in a new tab where you can add widgets to the page. Note: it is a good idea to save all your work on the page first, then open the Experience Editor. When you've saved your work in the Experience Editor and come back to the Content Editor it is a good idea to click off the page and come back to it. For unknown reasons this can prevent Sitecore thinking you are working on the same page simultaneously and end up overwriting the work you've done in the Experience Editor.
Preview - see a preview of your page.
Versions - on certain page templates: editorial (full width) article pages, list pages, form pages, you can view all previous versions of that page, view who last worked on a page, and when. This can come in handy if you need to retrieve copy from an earlier version. Note: Landing pages do not retain copies of previous versions.
Remove icon - removes the current version of the item you are on, in only the language you are in.
Remove (dropdown menu) - removes all the versions of the item of the language you are in. You can use this if you see a page accidentally has another language version attached to it when it shouldn't.
Language (dropdown menu) - shows you what language you are currently in and the dropdown menu shows you all available languages and whether that language has a version of the page.
Template Change - changes the template of the page. There will be a lot of warnings given when changing the template. This just indicates that you will lose certain widgets and functionality of the page your changing from. Not to worry - go ahead. If you change the template back, the widgets should still be there.
Details - this section is basically a summary of everything that's happened in the Experience Editor. It lists out which widgets are on the page. Under the Shared layout it lists which items are used on all language pages, under Final layout which items only on this language page. It is recommended to work only in the Final layout as to avoid mixing up widgets with other language versions.
Click and open a specific widget in the list and you'll see the path of the widget. This is very helpful to track down where the widget can be found in the Repository. If you want to change the widget item (not change the widget type!) you can add a new path in here instead of going through the Experience Editor.
Reset - resets the page to its basic state, removes all widgets and components. Use with caution!
Preview - see a preview of the page in the Content Editor. Won't open a new tab.
The tick boxes in View all have to do with how your Content Editor displays certains items. No right or wrong, you can play around with it. Suggested settings as above.
Customize - customize your toolbar with the menu items you like or frequently use.