A Web Service is a standardized way for different applications to communicate over the internet. It allows software programs to exchange data and perform tasks regardless of the programming languages or platforms they use. Web services typically use protocols like HTTP and data formats such as XML or JSON to facilitate this communication. Web services are commonly used in various applications, enabling features like online payment processing, data retrieval, and integration between different systems. They play a crucial role in the development of APIs (Application Programming Interfaces), which allow developers to build applications that can interact with other services seamlessly.