Different companies have different processes. The one that you applied for seems to have some process in place (coding, Skype).
The references probably mean that you got positive feedback from the three rounds so far. Which means if you are interested in the job, you should put in effort into getting the right references, and getting the references right.
Do keep in mind that just because you have progressed to the next stage, you will not necessarily make it through. There could be various reasons for you to get on hold - they get an awesome candidate, or just want to see if an awesome candidate comes along.
Sometimes hiring is also preemptive. They might have people in the pipeline, but only make offers as they need them. Or a change in business conditions, or funding might result in a delay or cancellation of the offer.
The conclusion is - you made the next step. Send the references and wait (or follow-up after a decent interval).