When you enter two or more words on a search line, it will look for web sites that have any of the words on them. For example a search for France travel will locate all web sites with either the word France or the word travel. You might want to narrow the search down to Paris travel, or maybe just Paris. Using quotation marks can help you narrow down a search. Use lower case letters when typing in a subject for a search.
Most search engines give better results if lower case letters are used.
Typing candy AND sweets will retrieve all sites with the words candy AND sweets in them. Many engines automatically use OR for a list of words separated by spaces. Typing candy NOT chocolate will retrieve all sites containing the word candy which do not contain the word chocolate. Try several if you are not getting the results you need.