What is the difference between "keywords" and "search terms"?

In general, a keyword can consist of one or more search terms. However, these words are mostly used as synonyms , which means that their meaning is usually the same.

With Google, the keyword is what you can put in there so that your ad can be found for it, while the search term is what the searcher enters.

In other words, the searcher goes to Google, enters a search term in the search and Google shows a result where a suitable keyword has been stored.