A search for mnemonic system will return articles that have the words "mnemonic system" exactly in that order without anything in between.

If you want to search for articles that have words not necessarily together, use a comma to separate them. A search for mnemonic, system will return articles with both words somewhere inside.

You can combine these two search methods. A search for mnemonic system, link will return articles with the phrase "mnemonic system" and the word "link" somewhere inside.

Use the "Match" parameter to help find teasers. A search for clock, watch, time while matching "Any" will return articles with any of the three words.