Web Service: It's a stateless protocal. It work only HTTP .It doesnot mantation the session .It work only IIS service. UDDI:Universal Description, Discovery and Integration .UDDI is a directory for storing information about Web service.UDDI is a directory of Web Service Interface that are described by WSDL.UDDI provied information to web applications by using SOAP protocol.WSDL :Web Service Description Language, Which is used to describe a web service in term of messages that is creates and accepts.The WSDL document is an XML file That contain Interface  schema for the Web service. These are Elements in the WSDL documents(1)Types (2)Message (3)Service (4)Address (5) Binding .

WCF : Windows Communcation Foundation  It is a service based. It is flexiable because it service can be hosted in different type of application.IIS,SELF HOSTING, WAS,Managed WINDOWS SERVICE. Main Thing In WCF : Service,Hosting,EndPoint.

Service : Service Contract (1) attribute has to define the Interface (2)Opeartion Contract :  attribute used to define the method inside the interface . Data Contract :  used to define the class .Data Member : used to define the property, field, Fault Contract :Define which errors are raised by the service, and how the service handles and propagates errors to its clients.  Message contracts
Allow the service to interact directly with messages. Message contracts can be typed or untyped, and are useful in interoperability cases and when there is an existing message format we have to comply with.

EndPoint : Endpoint Fusion of Address,Binding, Contract.

Address --- Specifies the location of the service which will be like http://Myserver/MyService.Clients will use this location to communicate with our service.

Binding --- Specifies how the two paries will communicate in term of transport and encoding and protocols

Contract --- Specifies the interface between client and the server.It's a simple interface with some attribute.

Difference : Web service does not maintain the session , but wcf do (Relable session)

WCF is sort of web service which is used to build service oriented applications.
and its supported in the .NET Compact Framework version 3.5 and later versions.

WCF is different from Web service in a sense that web service communication works only on HTTP protocol while WCF communication protocol could be HTTP, TCP, MSMQ, UDP etc.
And other major difference is web service is hosted only on IIS while WCF is hosted in .NET 3.0 or later, IIS, Windows service or console app.

One more thing  to notice is web config entries in WCF are case sensitive.

web services shares business logic to the other applications over the web.with web service user can share his functionality to either applications or other platforms.

UDDI:if we want to share our web service globally our web service have to register under UDDI(Universal Description,Discover and Integrity).
WSDL:(webservice Description Language) it is a language ,it can be retrieved web service related information.