lxml is a powerful library in Python used for processing XML and HTML documents. It provides an easy-to-use API for parsing, creating, and manipulating these documents, making it a popular choice for web scraping and data extraction tasks. With its support for XPath and XSLT, lxml allows users to navigate and transform XML data efficiently. One of the key features of lxml is its speed and performance, as it is built on top of the libxml2 and libxslt libraries. This makes it suitable for handling large files and complex data structures. Additionally, lxml integrates well with other Python libraries, enhancing its versatility in various applications.