A general discussion of structures can be found here.
Vector
Direction
GeoCoordinates
Waypoint
Orbit
Orbitable
OrbitableVelocity
Body
Atmosphere
Vessel
Control
ManeuverNode
Engine
AggregateResource
DockingPort
Gimbal
Stage
Part
PartModule
Sensor
VesselSensors
LoadDistance
Config
FileInfo
List
Highlight
Iterator
Kuniverse
Terminal
core
Lexicon
String
PIDloop
SteeringManager