Truncation means you include a special character at the end of your search term which will broaden your search to include any word that starts with that group of letters.
behavio* = Finds not only the word flavor but also behaviour, behavior, behaviors, behavioral, and other variant endings.
child* = Finds the word child, along with childhood, children, etc. (This can also pick up personal names, like Childress or Childs, so your search result may be muddied when you truncate.)
Using a Wildcard in your search means you can insert a symbol anywhere in a search term not just at the end, like the example above.
wom?n = Finds both women and woman
Not all databases use truncation and wildcards, so check the Help pages for that database if you're not sure.