How does exploration work? What are relic and data sites?

Exploration means finding hidden sites with your probe scanner, then hacking containers inside them.

1. Fly an exploration frigate (for example the Magnate, Heron, Imicus, or Probe) with probe launcher, relic analyzer, and data analyzer.
2. Launch probes and scan down Relic and Data signatures.
3. Warp in and hack the containers with a short minigame, then scoop the loot.

Exploration pays more in dangerous space, so start in high-sec and graduate to wormholes with a group.