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At a café, you order a sandwich and receive it, or hear that it is sold out. Websites work in a similar way.
When you open a product page, your browser sends a request to the website’s server. The response contains the page or an error. A shopping app can also request an action, such as placing an order, and receive an order number. The main data sent with a request or returned in a response is its payload. A request and its response make a round trip.
One page may need several requests
A page may make separate requests for text, pictures, and prices. Each takes time and can fail, which is why a page may partly load or show missing information.