You can search for, or navigate to, the content item that you want to link to. Furthermore, you can set a “target”: open in the same browser window, or a new one. In general, it is considered good etiquette to always open internal links in the same window. Setting a descriptive Title for the link is helpful if the item you are linking to does not have a distinctive title of its own.
When linking to external sites, make sure you include the complete link, including the “http://” or “https://” part, otherwise it will be interpreted as a relative link within your own site. Again, you can set a Target and Title.
Opinions differ on whether you should open an external link in a new window or not; ask if your organisation has a policy on this.
This tab lets you create a mailto: link, which will open in the user’s email program. You can optionally set a subject for the email, although your visitor will always be able to override it. setting the Email Subject is more a helpful suggestion.
Anchors are like position markers within a document, based on headings, subheadings, or another style set within the document. You can also set Anchors at arbitrary positions in a document.
Plone automatically creates Anchors for headings and subheadings, and thus you can directly link to a chapter in a long web document.