The document discusses .NET object serialization. It describes serializing objects to streams using binary and SOAP formatters. Binary formatters serialize objects to a binary format stream, while SOAP formatters serialize to an XML file. Formatter classes are used to control serialization and deserialization of objects to and from a stream. The stream carries type information to allow reconstruction of the object. The two main formatters that inherit from the IFormatter interface are the binary formatter and SOAP formatter. Examples are provided for serializing and deserializing objects using both formatter types.