A parser is a software component that interprets and processes input data, typically in the form of text or code. It breaks down the input into manageable parts, often called tokens, and analyzes their structure according to predefined rules. This is essential in programming languages, where the parser helps convert source code into a format that can be executed by a computer. In the context of web development, a parser can also refer to tools that read and extract information from HTML or XML documents. For example, a HTML parser processes web pages to enable browsers to display content correctly. Overall, parsers play a crucial role in data processing and programming.