Shown in the upper part of the dialog is the list of your project templates. When you select a template, its description is shown in the lower part of the dialog.
To delete unnecessary templates, select the templates and click 
(alternatively, press ⌘⌦ or ⌘⌦⌘⌦ or ⌘⌦⌥ Delete, ⌥⌦ or ⌥⌦).