An asterisk may be used to represent zero or more characters in a search expression. For example, searching for contract* will find not only contract but also contracts and contractual.
A question mark may be used to represent a single character in a search expression. That is, searching for ho?se will find both house and horse.
Quotations will search for the exact phrase. So searching for "small car" will not find small blue car, while searching without quotations for small car will return any segments containing the word small or the word car.