1. API
   1. Application Programming Interface
   2. Set of functions that allows an application to interact with external applications, operating systems, microservices, or data.
2. API Testing
   1. Checking whether the API meets expectations in terms of:
      1. functionality
      2. reliability
      3. performance
      4. security.
3. API Orchestration
   1. API orchestration layer is an abstraction layer that collects data from one or more services and prepares them in favor of client applications.
4. API Version:
   1. API versioning tracks changes in the API.
   2. Proper versioning supports maintenance and tracking.
5. API Gateway
   1. A single entry point for all clients.
6. API Deprecation
   1. State where the API is deprecated (no longer used).
7. API Keys
   1. The unique code used for authentication of the API.
8. API Request
   1. API request is the set of details needed to submit to the server to understand and respond properly.
9. API Response
   1. After sending the details as a request, the server interprets and sends the response back to the client.
10. API Virtualization
    1. API Virtualization is the process of mirroring your production APIs that promotes testing efficiency.
11. API Documentation
    1. The complete set of technical information and capabilities of the API.
    2. It carries all the sufficient information to work with that API.
12. BaseURI
    1. Base Uniform Resource Identifier is the complete path used to locate a specific resource.
13. Contract
    1. An agreement details what the consumer can expect from the API.
    2. It details how the API works.
14. cURL (Client URL)
    1. cURL is a command-line tool for transferring data from or to a server designed to work without user interaction.
15. Composite APIs
    1. Composite APIs are the combined APIs that help us access several endpoints through a single API call.
16. GraphQL
    1. GraphQL is an application-level query language and runtime for APIs.
17. HTTP methods
    1. An HTTP (HyperText Transfer Protocol) request is an action to be performed on a resource identified by a given Request-URL.
    2. The most common ones are: GET, POST, PUT, and DELETE.
18. HTTP Headers
    1. Headers are the additional but essential information sent as part of the request details from the client for the server to understand the client.
19. JSON (JavaScript Object Notation)
    1. JSON is an open-standard file format or data interchange format in human-readable style.
20. Microservices
    1. A modular software component that does one defined job.
    2. They are small, independent, and loosely coupled.
21. MQTT (Message Queuing Telemetry Transport)
    1. Commonly used messaging protocol for the Internet of Things (IoT).
    2. MQTT allows for messaging between devices to the cloud and the cloud to the device.
22. OAuth
    1. OAuth is a delegated authorization framework used for REST/APIs.
    2. This is one of the efficient methods of authorizing, which restricts the improper usage of the APIs.
23. Parameters
    1. API Parameters are passed along with the endpoint URL, which helps filter resources.
24. Public APIs
    1. An open or public API saves developers time by allowing them to connect their platform with previously existing tools, reducing the need to create entirely new functions.
25. Private APIs
    1. Internal APIs are the opposite of open APIs in that they are inaccessible to external consumers and only available to an organization’s internal developers.
26. Payload
    1. The actual body/content passed as part of the API request.
    2. It can be in different forms such as JSON, Text, HTML, XML, etc.
27. Postman
    1. Postman is a platform to build, test, design, modify, and document APIs.
28. REST (REpresentational State Transfer)
    1. One of the most popular types of API due to its simplicity and client-friendly nature.
29. Schema
    1. It defines the data format, including the data types.
30. SOAP (Simple Object Access Protocol)
    1. SOAP is an XML-based protocol for accessing web services over HTTP.
    2. The SOAP message is nothing but an XML document with the envelope, header, and body.
31. Status Codes
    1. The list of numeric codes followed by a message returned from the server to the client.
    2. Each response code tells a different story about the API response.
32. Swagger
    1. Swagger is an open-source set of rules, specifications, and tools for developing and describing RESTful APIs.
33. Webhook APIs
    1. A webhook is a lightweight API that powers one-way data sharing triggered by events.
34. WebSockets
    1. A WebSocket is a transport protocol defined by a persistent bi-directional communication channel between a client and the server.
    2. It was designed to overcome the limitations of HTTP’s basic request/response mechanism.
35. Based On MuukTest's blog article on Lexicon for API Testers by Pricilla Bilavendran
36. Mindmap by Rahul Parwal