If you are not familiar with the HTML hyperlink tab <a>, go first read anchor text and how to make hyperlink open in new window or tab and/or making active (clickable) hyperlink in posts and comments. Please take note that the target attribute has been deprecated and will not pass W3C XHTML 1.0 Strict validation. So if W3C validation is important to you, you should not use the target attribute.
To make hyperlink open in new tab or window, one uses either the target="_blank" or target="new" or target="anything" where anything is exactly that, any word, even meaningless one like "abtjsgj". Now I have received query what is the difference between them. Before publishing this post, I have tested the hyperlinks with different attribute at testing target attributes for hyperlinks where you can try out the links yourself.
When you use the target="_blank" attribute for the hyperlink <a> tag, all links with that attribute will open in new windows or tabs. When you use the target="new" or target="anything" attribute, the first click on any link with that attribute will open in a new window called new or anything. Any subsequent click on any link with that attribute will open in the same window called new or anything.