What is a web service?

A web service is defined as a system that enables different programs to communicate and share data over the internet. This facilitates interoperability between various software applications, regardless of their underlying platforms or programming languages. By adhering to standards such as HTTP, XML, SOAP, and REST, web services allow for seamless integration and interaction between disparate systems, enabling them to function together effectively.

The choice that identifies a web service as a mechanism for interaction between multiple applications aligns with this definition, highlighting its role in enabling distributed computing and application integration. This capability is increasingly important in today's interconnected world, where applications must often share and utilize data from different sources.

In contrast, options that describe a web service as a security feature, a programming language, or a tool for monitoring server performance do not accurately capture the essence and functionality of web services. Security features protect applications, programming languages are the mediums for development, and monitoring tools track system performance rather than enabling communication between systems. Thus, recognizing the primary purpose of a web service as facilitating interactions between programs is key to understanding its significance in software development and architecture.