Web scraping means automatically retrieving information shown on websites. A program reads the pages for you and files what it finds into a table.
The idea is simple. Doing it cleanly, repeatedly, on sites that keep changing, is the hard part.
What it is for
An online retailer watches competitors' prices. A developer follows property listings in one city. A recruitment firm feeds its own job engine. A brand checks where its products are being resold, and at what price.
What these have in common: the information is public, but no button lets you download it in bulk.
What happens technically
The program requests a page, the way a browser would. It finds the useful parts (price, title, date), pulls them out, then writes them to a file or a database.
Some sites serve their content straight as HTML. Others build it in JavaScript once the page opens, which means driving a real browser. What you receive is the same either way. The work behind it is not.
What about the law?
We work with publicly accessible data, at a pace that does not disturb the sites we consult. Defining the use is your responsibility, and we advise you on it. If your project touches personal data, France's data protection authority, the CNIL, publishes practical guidance worth reading.
Scraping becomes worthwhile as soon as data exists online with no interface to retrieve it in volume or on a schedule. If that is your situation, tell us what you need.