It requires that special remote-access programs be running on both computers, and none of the many remote access programs is compatible with any of the other programs, because they all use closed, proprietary protocols. Furthermore, they usually require that the remote user be the sole user of the machine. X, by contrast, is designed to run remotely, and to run on multi-user systems. Because Wine translates Windows calls into X calls, Wine allows the same easy remote access that X does. It is also responsible for properly loading Windows applications.
Wine reads the executable file, and correctly loads the code, data, and resources into memory.
Wine was originally developed for Linux, but the port to FreeBSD and NetBSD took less than a week. The most basic window-handling functions in Wine are written as an interface to the appropriate Xlib functions for manipulating X windows. However, wherever possible, other internal functions in Wine call the basic window-handling functions in Wine instead of Xlib. When launched, programs run and act as if they were running under Windows. By default, applications come up in a special kind of window that looks very much like those provided by Windows instead of looking like other X windows.