Application Programming Interface: a defined set of rules that lets one piece of software request data or services from another.
An API acts like a menu in a restaurant. It lists what you can order and how to ask for it, without exposing how the kitchen works. Developers use APIs to connect apps to payment processors, maps, weather data, AI models, and countless other services.
For example, a weather app might send a request such as GET /forecast?city=Darjeeling to a provider's API and receive structured data, often in JSON, describing temperature and rainfall. Well-designed APIs are documented, versioned, and secured with authentication keys or tokens. Common styles include REST, GraphQL, and gRPC. APIs are also a business model: many companies charge for access based on usage.
A server that sits in front of backend services and handles routing, authentication, rate limiting, and monitoring for API requests.
API KeyA unique code that identifies an application or user when it calls an API, used to control access, track usage, and apply billing.
BackendThe server-side part of an application that handles data storage, business logic, and integrations, out of the user's direct view.
Function CallingA feature that lets a language model request a specific software function, with structured inputs, so an application can take an action or fetch data.
GraphQLA query language and runtime for APIs that lets clients request exactly the data they need in a single request.
InteroperabilityThe ability of different systems, devices, or applications to exchange data and work together without special effort from users.
JSONJavaScript Object Notation: a lightweight, text-based format for storing and exchanging structured data.
Model Context ProtocolAn open standard, known as MCP, that defines how AI applications connect to external tools, data sources, and services in a consistent way.
OAuthAn open standard that lets users grant an app limited access to their data on another service without sharing their password.
Open BankingA system in which banks securely share customer financial data with authorized third-party apps through APIs, with the customer's consent.
REST APIAn API that follows Representational State Transfer principles, using standard HTTP methods and URLs to work with resources.
Rate LimitingRestricting how many requests a user, device, or application can make to a service within a set time period.
Robotic Process AutomationSoftware bots that mimic human actions on a computer, such as clicking, typing, and copying data, to automate repetitive tasks.
Software Development KitA packaged set of tools, libraries, documentation, and code samples that helps developers build software for a specific platform or service.
WebhookAn automated message one application sends to another via an HTTP request when a specific event happens.
XMLExtensible Markup Language: a text-based format that uses custom tags to structure, store, and exchange data.
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