Introduction to API

What is an API?

The term API stands for application programming interface. API is a set of routines, protocols, and tools for building software applications. In simple words, we can define API as the messenger that delivers your request to the provider that you’re requesting it from and then delivers the response back to you and allows two applications to talk to each other.

Let’s understand the application programming interface architecture in detail referring to the diagram.

API or Web Service

Web Services

In simple words, web services are XML-centered data exchange systems that use the internet for A2A (application-to-application) communication and interfacing. These processes involve programs, messages, documents, and/or objects.

  • Essentially same as API
  • All web services are API’s but all API’s are NOT Web services
  • Web Services requires a Network to operate opposite to API’s
  • Web Services- SOAP/ REST. XML-RPC
  • Web Services slower than API


  • Platform Independent
  • Fast to retrieve data
  • No Front end required to Test the feature
  • Extremely helpful in Creating Microservice architecture

Types of API

REST API stands for Representational State Transfer. It has the following properties –

  • Architectural style with loose guidelines and recommendations.
  • Stateless (no server-side sessions).
  • API calls can be cached
  • Plain text, HTML, XML, JSON, YAML, and others
  • Open Source
  • Less Secure but fast and flexible

SOAP API stands for Simple Objects Access Protocol, It is a web communication protocol with the following properties. Standardized protocol with pre-defined rules to follow.· Stateless by default, but it’s possible to make a SOAP API stateful.· API calls cannot be cached· Supports the only XML· Not Free· More Secured, standardized.

Why SOAP is prefered more over REST API?

  • Enterprise Level
  • Highly Secured Application
  • More Complex Applications Eg: banking, payment gateways, CRM, Telecommunication.

In our next upcoming post, we will learn about the importance of API testing. Please tell us about your API knowledge before-and-after reading. I bet you’ll have something to say!!!
Happy Learning

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