A small arrow beside a heading reveals an explanation when clicked. That interaction can be provided by a built-in HTML disclosure element rather than a separate page request.
Recognise the basic structure
The HTML details element, usually paired with summary, provides an expandable disclosure. Its content can already be present in the document while the closed state keeps it out of the ordinary visual flow.
Avoid guessing the implementation from appearance
Other widgets can look similar while using scripts or loading additional content. If the difference matters for troubleshooting, inspect the actual element and network activity. A visual arrow alone cannot tell you how every site implemented its panel.
For someone writing a help page, the practical lesson is to choose a summary that describes the hidden material clearly. “Delivery times” gives a reader a better reason to expand than “More”. Essential instructions should remain easy to discover, and the interaction should be checked with keyboard navigation as well as a mouse before publication.