Final answer:
The script tag is used to let the browser know that it is about to see JavaScript code.
Step-by-step explanation:
The tag used to let the browser know that it is about to see JavaScript code is the script tag. This tag is placed within the HTML code and is used to embed or reference external JavaScript files. It can be placed in either the head or body section of an HTML document, but it is generally recommended to place it just before the closing tag for better page performance.