A customer using an online e-commerce store to buy a phone would generally type those words in the search box at the top of the site. As soon as you type your search query, the search results are displayed at the bottom, and on the left-hand side of the page you get a list of categories that you might be interested in based on the search text you just entered. The sub-search categories are shown in the following screenshot. How did the search engine figure out these sub-search categories just based on the searched text? Well, this is what clustering is used for. It's a no-brainer that the site's search engine is advanced and must be using some form of clustering technique to group the search results so as to form useful sub-search categories:

As seen in the preceding screenshot, the left-hand side shows the categories (groups) that are generated once the user searches for a term such as car
. The left-hand side looks quite relevant as we are seeing sub-categories for car accessories...