A wild card is a character that can be used in a search to represent unknown characters, words, or phrases. The most common wildcard is the asterisk -- *. It can be used in a search to represent zero or more characters.

The asterisk can be used as a kind of fill-in-the-blanks for Google searches. For instance, if most people who are searching for the person who invented the sandwich, will type in invented sandwich or who invented the sandwich. This will bring up a list of information, which may or may not contain the name of the inventor. However, if you search for the sandwich was invented by *, the name of the inventor will likely be one of the top three choices.

At the present time Google only supports searches where an asterisk indicates a whole word or phrase.

 The asterisk is even more useful when you are searching for things on your computer.  In this case it can be used to indicate a part of a word. For instance, using the Windows search to search for *.jpg will return a list of all the pictures on your computer that have the jpg extension. Searching for  j* will give you a list of all the files that begin with the letter  j.  Searching for *j* will give you every file that has a j in it.

 The question mark can also be used as a wild card, but it can represent only one character, so for the average user, the asterisk is much more useful.