Planets
Homeworlds are either a planet orbited by a large moon, or two planets orbiting each other. These planets are located fairly close to the sun, but have a protective atmosphere which allows colonists to survive on the planet's surface. Typically, 50% or more of the surface of the planet is covered in water. These planets environments are so favorable, that they were all colonized long ago. Population pressures are now causing colonists to flee these homeworlds in search of land that they can claim for themselves.
Arid/Frozen Planets are smaller planets with thin atmospheres. Water is typically found only at the poles or in underground ice veins. Despite the harsh conditions, colonists often find that these planets can be terraformed into a liveable state, especially if they are not too far from the sun.
Gas Giants are extremely large planets with thick hydrogen atmospheres and liquid hydrogen surfaces. Although their composition and high gravity make these planets uninhabitable, they are usually orbited by one or more moons which are large enough to have their own atmosphere and be suitable for colonization.
Asteroids are large chunks of rock which orbit the sun. Some asteroids may be as much as 1,000 km in diameter. Colonists tunnel rooms and corridors in these chunks of rock, and turn them into cities.
Empty Space is any area of space without a significant feature. There may be tiny asteroids or uninhabitable planets in these locations, but as they are not relevant to ship captains, they are not displayed on ships' maps.
Wormholes
Universal Wormholes are wormholes that can be used by any ship.
Race-Specific Wormholes are wormholes that can be used only by ships built by a specific race. You will only see race-specific wormholes that are usuable by the ship you are commanding.
Ships
Human Ship A ship built by humans.
Bug Ship A ship built by bugs.
Robot Ship A ship built by robots.
Old Ship A ship built by the old ones.