In software development, two confusing terms for beginners are web services and API. At first, we can differentiate between these two terms and then can discuss more regarding web services. An API(Application Programming Interface) is a set of functions and procedures, that is used for creating software that can interact with existing applications. Likewise, a web service is a software system that helps for communicating between client and server applications through the Internet using open protocols. In other words, a web service is a standard XML-based information exchange system for direct application-to-application interactions. When comparing both the API and web services, we can conclude as web services are a subset of API.

Now, we can explain more about web services. As you know, web services are web application components that can be published, found, and used on the Web. This software system is interoperable and it can run smoothly on a variety of platforms and frameworks. Also, these web services are not restricted to any specific operating system or programming language(Java, .Net, Angular JS, Node.js, etc...). In web services, XML is used to code/decode the data and then transport it using any open protocol. The different types of web services types are:

• SOAP (Simple Object Access Protocol): SOAP is the XML-based messaging protocol that can be used for easily communicating between applications built with various programming languages. This light-weight protocol is suitable for accessing web services over HTTP.  This platform-independent protocol will reduce extreme development efforts. Exchange documents, call a remote procedure, broadcasting a message, and invoking remote methods are important features.
• WSDL (Web Services Description Language): WSDL is the standard format developed by Microsoft and IBM for describing a web service. This is a combination of SOAP and XML Schema and it is used for information exchange in decentralized and distributed environments. The WSDL will describe how to access a web service and what all operations are performed.
• UDDI (Universal Description, Discovery, and Integration): UDDI is a platform-independent, open framework that communicates via SOAP, CORBA, Java RMI Protocol. UDDI contains a registry of all web service metadata and a set of WSDL port type definitions.
• RESTful (REpresentational State Transfer): The RESTful web services will help web applications developed with different programming languages to communicate with each other. The underlying protocol of this lightweight, maintainable, and scalable web service is HTTP.