{{[[Bản mẫu:{{{1}}}|{{{1}}}]]}}
tltt stands for "template link with tooltip". "tt" also can stand for the <tt> tag that surrounds it.
Like {{tl}} (see documentation), with an additional parameter for the tooltip. This will be displayed when user hovers over the curly braces. (Try it right here: {{Any template}}!)
The template is meant to be used in pages such as {{TestTemplates}}, where it is desirable to provide a bit more explanation for a template than what its name reveals.
Differently from {{tl}}, the font is set in monospace, so that all text appears in non-proportional font.
The template also permits up to two named parameters, like so:
{{tltt|Tên bản mẫu|Tooltip text|par=Tham số thứ 1=1|par2=Tham số thứ 2=2}}
Kết quả: