Truncation is used with root words to express multiple endings, e.g. cold* would find cold, colder, coldest
Wildcard are used within words to find words spelled differently but have the same meaning, e.g. labo?r would find labor or labour
Truncation and wildcards vary from database to database. Check the database Help page to find out what to use in your search. Common truncation/wildcard symbols include: *, #, ?, $, !. You must find what symbol each database uses and how they use that symbol, you may not be getting the results you expect if you don't do this.
Warning: when using truncation make sure to use enough of the root word to express your idea, use too little and you will get bad results, e.g. if you are looking for articles on therapy: therap* = good (therapy, therapist, therapeutics...), the* = bad (theology, thermal, thespian...)