Webchanges is an application that monitors parts of webpages for user-relevant changes.
For each collection of webpages, the user has to write a so-called monitor file once. This file describes, which documents on the web belong to the collection being monitored, and which parts of these documents are relevant.
A single relevant part of a document is called monitor.
To be pedantic, webchanges operates on the [X]HTML-parts of a webpage only (leaving images, animations, etc. out) and uses W3C’s XPath 1.0 embedded in its own language to select those relevant parts.