Foren / Cotonti / Support / Downloaded theme, different langage

In this particular theme - no, it seems like it's simply text in the TPL file.

Some themes use language strings for everything, which is the better approach.
You can follow this approach and add new strings to the glow.en.lang.php file like so:

$L['thisissomething'] = 'This is text';

And then include the string in the TPL like this:

{PHP.L.thisissomething}

This way you can make the website multilingual, and put the same strings in for example glow.es.lang.php, with the text in a different language ofcourse.