By default, the IncrementalSearch property is exDefaultStartWith, and it is similar with incremental searching in the Windows Explorer. An incremental search begins searching as soon as you type the first character of the search string. So, typing characters starts searching for objects. If no character is typed during one second, the incremental search ends. If the IncrementalSearch property is exStartWith or exContains, the control highlights the found characters, while typing as shown in the following screen shots. The exStartWith option searches for objects that starts with typed characters while, the exContains option searches for objects that contains typed characters. Once an object is found and highlighted you can press F3 key for searching the next occurence.  

The picture shows the Prog word as being highlighted after the user typed "prog" characters. In this case the IncrementalSearch property is exStartWith

The picture shows the Files word as being highlighted after the user typed "files" characters. In this case the IncrementalSearch property is exContains