Wreckages appear when ships or stations are destroyed. A destroyed ship will transform into wreckage once its health reaches 0. They can also be created by destroying only parts of a ship. The destroyed part might break off and form a wreckage.
Wreckages can be created by the procedural generator, when generating a new sector.
The player can destroy the wreckages and collect credits from them. blocks made from a certain material will drop resources of that material type on destruction. Occasionally, the cargo bays may still hold cargo, which can be sold for a profit. Also, destroying wreckage tends to yield more modules and turrets than simply salvaging them (*).
Players can salvage wreckages with salvaging lasers to gather resources. The amount of resources you get from mining or salvaging depends on the efficiency of the turret.