In addition to the answer by Manfred: this is some basic explanation of real time.
Hard real time system is the system where the maximum latency of some time-critical response can be found in advance, and the system must guarantee 100% probability of completion of the response in this time frame. This is pretty hard to achieve in principle. This is not about certain time itself, this is about the guarantee of response in time.
In one typical scenario, some part of throughput is sacrificed to the guarantee. The whole idea of hard real time is always related to the control of some hardware and processing driven by a hardware interrupt.
If you think about Windows in general you will understand that the hard real-time properties have nothing to do with Windows. Even if you apply real-time priority for a Windows thread/process, it won't guarantee certain predictable latency as this latency will depend on current operational status of the system (more or less busy with other priority threads, status of the cache of all levels (important limiting factor!) and stuff like that. If Ethernet is involved (set aside absolutely non-deterministic Internet), it's always introduces some probability of unlimited delays, as Ethernet architecture of resolution of clashes is totally based on a non-deterministic algorithm. Theoretically speaking, its possible to guarantee some slower hard real-time networking for a network with fixed number of players by scheduling and throttling all players in order to avoid conflicts; it should be based on some single central arbitrator device.
Everything outside the realm of hard real time is called soft real-time or something like that. I'm not sure if there is a commonly accepted and valid classification of not hard real time systems.
See
http://en.wikipedia.org/wiki/Real-time_computing[
^] and
http://en.wikipedia.org/wiki/Real-time_operating_system[
^].
Sometimes people call real-time something very specific. For example, there is a common term "real-time" applied to some important sub-system, such as related to multimedia. Needless to say that a media player, for example, should guarantee the fixed audio tempo and/or fixed frame rate. In this sense, it is really a hard real-time subsystem but— until the user does something active and CPU time consuming in parallel. In real life that video may start stalling. This is kind a real time but not of the true kind. True hard real time is used it military, transport systems and the like.
—SA