As others have stated, an informal greeting meaning "Hello, how are you?". But the true spelling should be Trix (with a capital T) because of its origin, which no
one seems to know: It was (still) an informal greeting, started in the early 20th century; but the entire phrase was "How are Trixie and the kids?"... basically asking how
one's family was doing. Trixie was short for Beatrix, or Beatrice (a
popular female name of the era) and came to be known as slang for "the wife". Over
time the phrase was shortened to simply "How's Trix?"
"Hey Rob, long
time no see. How's tricks?" ... "Doing
well Joe, thanks." (Incorrectly spelled there on purpose to satisfy
UD - use Trix)