What is the difference between XSD and WSDL?

WSDL (Web Services Description Language) describes your service and its operations - what is the service called, which methods does it offer, what kind of in parameters and return values do these methods have?

It's a description of the behavior of the service - it's functionality.

XSD (Xml Schema Definition) describes the static structure of the complex data types being exchanged by those service methods. It describes the types, their fields, any restriction on those fields (like max length or a regex pattern) and so forth.

It's a description of datatypes and thus static properties of the service - it's about data.

XSD defines a schema which is a definition of how an XML document can be structured. You can use it to check that a given XML document is valid and follows the rules you've laid out in the schema.

WSDL is a XML document that describes a web service. It shows which operations are available and how data should be structured to send to those operations.

WSDL documents have an associated XSD that show what is valid to put in a WSDL document.

XSD is to validate the document, and contains metadata about the XML whereas WSDL is to describe the webservice location and operations.

XSD (XML schema definition) defines the element in an XML document. It can be used to verify if the elements in the xml document adheres to the description in which the content is to be placed. While wsdl is specific type of XML document which describes the web service. WSDL itself adheres to a XSD.

If someone is looking for analogy , this answer might be helpful.

WSDL is like 'SHOW TABLE STATUS' command in mysql. It defines all the elements(request type, response type, format of URL to hit request,etc.,) which should be part of XML. By definition I mean: 1) Names of request or response 2) What should be treated as input , what should be treated as output.

XSD is like DESCRIBE command in mysql. It tells what all variables and their types, a request and response contains.

XSD is schema for WSDL file. XSD contain datatypes for WSDL. Element declared in XSD is valid to use in WSDL file. We can Check WSDL against XSD to check out web service WSDL is valid or not.