The * Wildcard
This wildcard represents any number of characters in that position.
For example, if you put the criteria as *Mart*, Excel will search for all entries which contains the work Mart; so it could be Martin, FoodMart, etc.
The ? Wildcard
This wildcard represents a single character in that position.
For example, if you put the criteria as Mar?, Excel will search for all entries which have Mar as the first 3 letters and then any 1 letter; so it could be Mark, Mart, Mars, etc.
You can use these wildcards while putting in the criteria using Advanced Filter.