The way parse works is quite straightforward. It's a function that takes an input to parse, and a set of rules to parse the input with—parse input [rules]

The input is the data that needs to be processed; it can be any series value. This is in most cases a string, perhaps coming from a web page, an XML or JSON or other type of file, or a spreadsheet, but it could also be a block with values, a binary value, or even code.

Parse searches the input and tries to pattern match it from start to finish with the rules. If the complete input until the end matches the rules, true is returned; if not, parse returns false. In fact, the rules block can be a complete subprogram, extracting information from the input, and processing that as well: