When you work manually with a windows application or a website, you wait until the application is ready for input before typing, you wait until the web page is loaded before clicking a link, etc...
A WinTask x64 script needs to behave the same way and Wait Functions are designed for this purpose.
Note that UseWindow function waits until the specified window is there before executing next step, and so you do not have to use a Wait function for waiting a new window to appear. UsePage function waits until the specified web page is fully loaded before executing next step, and so you do not have to use a Wait function to test if the new page has finished loading.
This section describes the Wait functions available in WinTask x64.