Practically any element on your website can link to one of your webpages, another website, an email address or a downloadable file. Once an element has been clicked on, the quick bar, that appears above the element, has a link icon on it. Clicking this link icon brings up options to link the element to one of your website pages, a different website altogether, an email address or uploaded file. Also, at the bottom of these options is a check box for choosing if you want the element to trigger the link in a new tab.
It is common to keep links within your own website within the same tab, but when linking to another website to open it in a new tab. This keeps your website open in the visitors background and lessens the chance of them forgetting about your great site and navigating off somewhere else!