XML-RPC is a protocol that allows different software applications to communicate over the internet. It uses XML to encode its calls and HTTP as a transport mechanism. This means that one program can send a request to another program, asking it to perform a specific action and return a result. The simplicity of XML-RPC makes it easy to implement and use. It supports various programming languages, allowing developers to create applications that can interact with each other regardless of the language they are written in. This interoperability is beneficial for building web services and integrating different systems.