Very often it is useful to have one link, on a WordPress post, opens in a new tab.
In this way the user can download a file or see another site/post without loosing the article he is reading and so he can easily come back to it again, in the line he was, clicking on the previous tab.
To set that option, obliviously you can go in the text tab, available in the WordPress editor, and write the appropriate html, that is:
<a href="www.siteToLink.html" target="_blank">Text</a>
but you can do it even with the user interface,as you can see in the following. You only have to go in the settings page of the link form and set the “Open in a new tab” option: