Here's the basics of the models, listed in order of oldest to newest:
F200 - indoor desktop camera. Now retired and unavailable for purchase.
R200 - suited to indoors and outdoors. Best at scanning larger objects and the human body. No longer supported by the RealSense SDK but still usable with the older '2016 R2' SDK.
SR300 - indoor desktop camera. The next-generation successor to the F200. Suited to scanning small objects.
ZR300 - next generation successor of the R200, can be used indoors and outdoors, and perform robotics navigation operations such as SLAM. Multiple ZR300's can be used without them interfering with each other. Only usable with Linux and Librealsense or the RealSense SDK For Linux (which has Librealsense incorporated into it as a module).
D415 and D435 - indoor and outdoor cameras being released in September 2017. Contains the most powerful RealSense technology yet, with real-time sensing suited to autonomous vehicles. Will use a new RealSense SDK software that is not compatible with previous SDKs.
Are those chips/PCBs, or a completed working cameras?
All of them can be bought as cased working cameras. The D415 and D435 are not in Intel's official online store yet, but the R200, SR300 and ZR300 are.
There is a new message on the front page of the store today, saying that with the introduction of the new D-cameras, Intel is transitioning away from the R200 and SR300 (but apparently not the ZR300) and so is offering discounts.
RealSense cameras can also be purchased as PCBs without cases through any Intel Approved Distributor company, as Intel do not sell these versions themselves directly.
I have to go 'off shift' for the day now sadly, but will pick up any new questions you leave here at the start of Monday morning. thanks for your interest in RealSense!
Those are very helpful info for new comers like me! What are the corresponding PCB models? I am more interested in the PCBs.