When does a stream pipeline run?

A stream is a pipeline of steps over a collection. peek runs a side action on each element, and collect ends the pipeline and gathers the result. What does this print?

Stream<String> s = Stream.of("a", "b")
    .peek(x -> System.out.print("peek " + x + " "))
    .map(String::toUpperCase);
System.out.println("no terminal yet");
System.out.println(s.collect(Collectors.toList()));