The t:trans attribute is an alias of the trans Symfony tag and allows you to translate the content of a node.

Let’s see how does it work:

<div t:trans="">
    Hello world

This option will allow Symfony to extract and translate the “Hello world” sentence.

Of course, you can also use any variable inside your text.

<div t:trans="{'%name%':'John'}">
    Hello %name%

You can also specify different domains for your translations.

<div t:trans="{'%name%':'John'}, 'app'">
    Hello %name%


See here to learn more about the Symfony translation system.