The primary purpose of structure is to hold your ship together. There are 4 types of structure in the game. When parts are destroyed, structure is left behind.
As of Cosmoteer 0.12.11 structure parts can be self-destructed. This allows them to be used to separate a child ship from the mothership.
|1x1||1x1 wedge||1x2 wedge|
Structure behaves much differently from other parts. Its the only part which uses structural health type. When hit by a projectile, the projectile will damage the structural health and continue on its path. Missiles are the exception, and will detonate on hit.