Z-level
Z-Level refers to the various maps with set borders that contain the playable areas of SS13. Moving off the edge of a z-level in space will take you to one of 2 z-levels at random (including possibly looping back to the one you just left). Certain z-levels contain interesting items and gear for the adventurous space explorer.
Station
This is the level that all crewmembers except miners start on. It contains the main space station and the Syndicate Teleporter. Once you have left it, this z-level is only accessible by the Mining Shuttle, pods with proper navigation technology, and by teleportation.
Mining
This level is immediately recognizable by the many asteroids, and contains the Mining Outpost and the Prison Station. Miners who do not join late will start here. The Mining Shuttle can be used to travel from the Mining Outpost to Engineering on the Station Z-Level. This level can be accessed through random space exploration.
Space
This level contains the remains of Zeta station, the remains of Donut station, the mysterious Hemera 7, the Soviet Derelict, and the Wizard's den. It can be accessed through random space exploration, and in addition, there is a teleporter beacon.
Centcom
This level contains a variety of places that cannot be reached through regular means. There is Centcom, which is accessible with the escape shuttle. The Maze is accessible through hacked VR pods and admin fiat. The Syndicate Shuttle is home to the Nuclear Operatives and can only be reached with a Syndicate Teleporter Remote.
The Void
Covered in a weird swirling energy and home to the mysterious void station. Can be accessed through random chance using Telescience.