[LYN-4366] Add API documentation for AzNetworking, Mutiplayer Gem, and Multiplayer Compression Gem classes.

Signed-off-by: stramer <stramer@amazon.com>

Code/Framework/AzNetworking/AzNetworking/PacketLayer/IPacket.h

@@ -24,6 +24,15 @@ namespace AzNetworking
 
     //! @class IPacket
     //! @brief Base class for all packets.
+    //!
+    //! IPacket defines an abstract interface that all packets transmitted using AzNetworking must conform to. While there are
+    //! a number of core packets used internally by AzNetworking, it is fully possible for end-users to define their own custom
+    //! packets using this interface. PacketType should be distinct, and should be greater than
+    //! AzNetworking::CorePackets::MAX. The Serialize method allows the IPacket to be used by an
+    //! ISerializer to move data between hosts safely and efficiently.
+    //!
+    //! For more information on the packet format and best practices for extending the packet system, read
+    //! [Networking Packets](http://docs.o3de.org/docs/user-guide/networking/packets) on the O3DE documentation site.
     class IPacket
     {
     public:

Code/Framework/AzNetworking/AzNetworking/PacketLayer/IPacketHeader.h

@@ -28,6 +28,19 @@ namespace AzNetworking
 
     //! @class IPacketHeader
     //! @brief A packet header that lets us deduce packet type for any incoming packet.
+    //! 
+    //! IPacketHeader defines an abstract interface for a descriptor of all AzNetworking::IPacket sent through AzNetworking. The
+    //! PacketHeader is used to identify and describe the contents of a Packet so that transport logic can identify what
+    //! additional processing steps need to be taken (if any) and what type of Packet is being inspected.
+    //! 
+    //! The PacketFlags portion of the header represents the first byte of the header.  While it can be encrypted it is
+    //! otherwise not exposed to additional processing (such as an AzNetworking::ICompressor).  PacketFlags are a bitfield use to provide up
+    //! front information about the state of the packet. Currently there is only one flag to indicate if the Packet is
+    //! compressed or not.
+    //! 
+    //! The remainder of the header contains the PacketType and the PacketId. While the PacketFlags byte is exempted from most
+    //! additional forms of processing, the remainder of the header is not.
+    
     class IPacketHeader
     {
     public: