Wildcards and Truncation are very similar... But Wildcards are really useful when there are multiple ways to deal with the middle of a word (as opposed to Truncation, which was only dealing with the ends of the words).
The "?" symbol is for when there is a single character in a word that could change (for example woman and women). The question mark is used instead of the character that could change, and this lets the search engine know that it should look for both.
Since this is a feature of the database, one thing to be cautious about is making sure not to end a search query with a “?” (if it is in the title you need to remove it to avoid problems)
The other character the the "#" sign, which tells the search engine to fetch results that have an additional extra character (which helps to retrieve words that have differences in spelling like color and colour).
This can be nice with some types of alternative spelling, but caution should be used with it since sometimes it might miss results that probably should have been included.