CCP Whisper heads up Team Bifröst -- developers tasked with making EVE a more dynamic setting, and introducing a sense of the unknown into the game. (In Norse mythology, Bifröst is a bridge leading between the realms of man and gods.) The way to do that is not through instances, as more than a few players theorized would happen. Rather, CCP has added thousands of new solar systems to New Eden, none of which can be found on the existing star map. They're only discoverable through true exploration.
Wormholes will open at different locations randomly and their inherently unstable nature means that once you venture within, you may find yourself in some far flung region of the galaxy with no simple way to return from where you left. You could have one hell of a journey trying to get back home again, or you might opt to follow the wormhole further into the unknown... Despite such dangers, the wealth and ancient technology that can be discovered in these hidden corners of the galaxy could make the rewards outweigh the risk, for some.
Beyond the new additions to EVE, sweeping changes to the existing game mechanics for exploration are in the works, CCP Whisper writes. The ways that players currently scan for anomalies in exploration, or scan down one another for more violent pursuits, are going to be very different in Apocrypha. For instance, scan probes won't simply be disposable and will be used much more dynamically than in the past. The new probes won't be fixed in one location once deployed. In fact, they will be able to warp to coordinates you specify in the solar system map. Revamping the existing exploration paradigm opens up a whole new can of worms in terms if CCP Games is completely displacing the old system with the new, but more information will be available as we get closer to the Apocrypha launch.
CCP Whisper's dev blog "Building a New Bridge to the Stars" is the first solid information the developers have released (outside of E-ON) about the Apocrypha expansion's features, and should pretty much be essential reading for any EVE Online player. Player response is largely positive so far, and there's an ongoing discussion between the playerbase and the devs on the forum thread linked to CCP Whisper's dev blog.