When you submit your query, the search engine will look up each word of the query in the index and construct a list of hits. Hits are pages that contain all of the words in your query.
If you perform an advanced search, additional filters are applied to the hit list. For example, if you search for documents in the .ac.uk domain only, pages from other domains will be excluded from the hit list.
Some search engines provide extra features. Most will check the spelling of the words you entered, and warn you if you make a spelling mistake (but remember that many web pages use American spelling). Some offer stemming, that is, including common grammatical variants. Some may search for common synonyms as well as the word you typed.
Replacing grammatical variants of a word by its root or stem; for example replacing 'searches' and 'searching' by 'search'.
Look at your favourite search engine. Which of these features does it offer? Look for the help pages or search tips.
4.3.1 Searching for images
When I searched for an image of a gorilla, was the search engine really recognising images of gorillas? The answer is no. Instead it was searching for the text 'gorilla' associated with the image – in the filename, in the alt text description or in the text surrounding the image on the web page.
Alt text is a description of an image for people who might have difficulty seeing the image itself. It can be seen when a mouse is passed over the image.