I was gifted a Nikon wireless speedlight commander SU 800 can anybody tell me can it be use with other flashes, than nikon or what it is compatible with
The Nikon CLS system (more properly called Advanced Wireless Lighting (AWL) when referring to the wireless aspects of the CLS system which also encompasses all of the Nikon flash system including the hard wired uses of flash) uses optical pulses to communicate with the off camera flashes. The source of the optical pulses is either an on-camera flash or on camera near-infrared controller. In either case the on camera unit must be a "Commander" in the CLS/AWL system. Your SU-800 Commander is a camera mounted near-infrared controller in the CLS/AWL system.
The nikon flashes that are controllable by the SU-800 are SB-R200, SB-600, SB-700 SB-800, SB-900 or SB-910. The SU-800 Commander also works with third party flash units that have built-in support for CLS/AWL. These would include certain units from a wide variety of third party flash manufacturers such as:
Metz (15 ms-1, 44 AF-1, 48 AF-1, 50 AF-1, 58 AF-1, 58 AF-2, etc)
Nissin (Di622 II, Di866, Di866 II)
Sigma (EF-500 DG Super, EF-530 DG Super, EF-610 DG Super)
Yongnuo (YN-460-RX, YN-560EX, YN-565EX, YN-568EX).
The specific models must be Nikon CLS/AWL compatible. Note that some of these models may be "manual power only" units that can be controlled manually with the SU-800 Commander but are not fully compatible with i-TTL, Auto FP, etc.
There is a "CLS compatible units manufactured by Metz, Nissin, Sigma, Sunpak and YongNuo" chart here that shows many Nikon compatible third party flashes. Those with an "r" in the WL column can be optically controlled wirelessly by the SU-800.
There are differences between an optical communication system, such as the Nikon AWL system used by your SU-800 Commander, and a radio communication system such as that used by most wireless triggers. Radio tends to have a greater range, doesn't require line-of-sight, can operate in very bright environments such as direct sunlight (that gives the optical system a tough time), and has the ability for more than one set of the same type to be used in proximity to one another without interfering with each other. (Think several press photographers all using Nikon covering an event for multiple publishers. Or more than one shooter at a wedding.)
Note that not all CLS compatible flashes can be controlled wirelessly by the SU-800 or any other Nikon commander flash. They must also support AWL. Many CLS third party flashes are not AWL compatible.
The SU-800 is a headless (has no flash lamp) commander unit in the Nikon CLS (Creative Lighting System) optical "smart" wireless system.
Therefore, all the flashes that can be used as slave units in Nikon's CLS optical system are compatible with it. This includes all the current speedlights in Nikon's lineup, like the SB-500, SB-700, SB-910, and SB-5000, as well as older discontinued models like the SB-600, and SB-800.
With non-Nikon third-party choices, it can get a little trickier finding out whether or not it's compatible, but what you're looking for is compatibility with CLS. This can get tricky, because a lot of 3rd-party flashes from makers like Sigma, Metz, Nissin, Yongnuo, Godox, Neewer, etc. etc. etc. also include "dumb" optical slave modes. These are different.
The "dumb" slave modes (most typically called S1/S2 modes) are simple sensor-based remote flash triggering, which can be set off by any flash burst--even that from the built-in flash on a P&S camera. This is not what you're looking for in the specs. The main distinction is whether or not anything besides the "fire" signal is communicated, such as TTL or HSS information.
Most typically in manufacturer specs and descriptions, you'll see some wording like "compatible with Nikon's wireless system" or "wireless TTL" but there's no set standard, so you may have to do some googling on a case-by-case basis as well as looking at specs.
Also, be aware that CLS is great for indoor/studio use, but can become a little less reliable and more stringent on range and line-of-sight, if used outdoors in bright sunlight, which is why most folks use radio triggers instead of optical slaving.
The Yongnuo YN-565N is one, which while it has S1 and S2 slaves modes, HOWEVER it also has a SL slave mode that works well with the Nikon Commander. See a review at http://www.scantips.com/lights/yongnuo565.html
If you want to spend $200 more or $500 more for a Nikon model, they will have a few little details you will like. But this Yongnou YN565N is a very nice flash for the money. It will do all you need done.