Here are the classes, structs, unions and interfaces with brief descriptions:

Bounds	Bounds is a 3-dimensional bounding box
ChannelData	ChannelData adds sample values to the ChannelInfo class
ChannelInfo	ChannelInfo stores the basic properties of a channel
DataTypeUtils	Helper functions for interaction with the DataType enum
Endian	Endian is a helper class that figures out the host's byte order
Error	Error is the base class for all LiDAR SDK errors
FileIO	FileIO implements file-based IO
IO	IO is the base class for binary input and output
IO::Location	Location is a helper structure for holding the location of data in a IO object
Metadata	Metadata is a container for storing metadata about the point cloud
MG4PointReader	MG4PointReader reads LiDAR-based MrSID files
Mutex	Mutex is a cross platform wrapper for mutexes
MutexMonitor	MutexMonitor use Resource Acquisition Is Initialization (RAII) to mutex lock blocks of code
Object	Object is the base class for implementing reference counting
OSError	OSError extends Error by using errno or GetLastError() to build the text description of the error
PercentProgressDelegate
PointData	PointData is a group of ChannelData objects
PointInfo	PointInfo is a group of ChannelInfo objects
PointIterator	PointIterator is the base class for accessing the point cloud
PointReader	PointReader is the base class for reading LiDAR file formats
PointSource	PointSource is the base class of LiDAR point cloud extraction pipeline
PointWriter	PointWriter is the base for writing LiDAR files
ProgressDelegate	ProgressDelegate is the base class for progress and interrupt reporting
Range	Range is a 1-dimensional interval
Scoped< TYPE >	Scoped is a wrapper class around Object that gives it block scoping
SimplePointWriter	SimplePointWriter handles some of the bookkeeping of writing a file
Stream	Stream is the base class for buffered input and output for IO objects
StreamReader	StreamReader implements buffered reads from IO objects
StreamWriter	StreamWriter implements buffered writes to IO objects
TXTPointReader	TXTPointReader reads LiDAR-based Text files
TXTPointWriter	TXTPointWriter writes LiDAR-based Text files
Version	Functions for geting the SDK version and MrSID file version