What is the purpose of the DOM in web development?

The purpose of the Document Object Model (DOM) in web development is to represent the structure of a web document in a hierarchical manner, enabling programming languages, particularly JavaScript, to interact with the content, structure, and style of the document. The DOM acts as an interface that browsers provide; it allows developers to manipulate elements, attributes, and text within the HTML or XML documents dynamically. This interaction is crucial for creating dynamic, interactive web applications where content may change in response to user actions or other events.

The other options focus on different aspects of web development that do not accurately describe the DOM's primary function. While defining styles is related to CSS, the DOM itself does not define styles but rather provides access to elements that may have styles applied to them. Managing web server communication pertains to technologies like AJAX or fetch APIs, which handle requests and responses between the client and server, not the DOM. Optimizing webpage speed involves techniques such as minimizing resources or leveraging caching, which are separate from the DOM's role of representing document structure and allowing interaction with it.