Form api questions – datas after the form

OK I understand how to display a select list and a submit bottom.
OK I understand also how to display “hellow world” in another module.

But I don’t understand how to have my “hellow world” or something more complex after my form, in same page. In the page callback I have my form, so I cannot in the same time have a function with a return t().

Drupal version: 


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