Not much, about the same as between "it" and "this".
Direct translation: Er dette korrekt? In casual use, this would be a bit more appropriate and less formal: Er det her rigtigt?
"How are you?" - Hvordan har du det? "How are you in Danish?" - Hvordan har du det på dansk?
Did you mean: "How do they SAY "that is what friends are for"? in danish?" Anyway, it is called "Det er det, man har venner til" :-)
" Hvordan har du det? " is how you say "How are you?" in Danish.
Hvordan går det
Det var så lidt.
det var godt
Ha' det sjovt.
hvordan har du det??
Det er en bog.
Det her er mit arbejde.
Det regnede i dag.