Windows Phone 8.1 is the massive OS update from Microsoft. Lumia Cyan is the corresponding firmware from Nokia, customized for individual hardware. The two go together and are part of the official over-the-air update expected later in July and rollout through August.
Popular internet leaker @Evleaks has posted what looks to be a schedule of the Lumia Cyan update, broken down by device e.g. Lumia 920 and Lumia 1520. However, this is only for the Benelux region, which is comprised of Belgium, the Netherlands and Luxembourg.