Hi, Edward.
With view cameras, there is not really a rigid "body" in the same sense as with other cameras. You basically have a lens and some film, with a flexible, light tight connector between them, called the bellows. The lens and film mount to what are called "standards". So, a view camera is comprised of a lens standard, a film standard, and a bellows at the very least. There is always a way of supporting the two standards and connecting to a tripod. On some cameras, this is a single rail. On others, it is a flat "bed" type of support that holds the standards and connects to the tripod. (Technically, the lens and film back mount to "carrier frames", the carrier frames mount to the "standards", and the standards mount to the bed or rail, but almost no one bothers to make this distinction, except for Sinar, which is the most "Lego-like" of view cameras. The carrier frames are decidedly separate parts that are easily removable on a Sinar; not so with most other view cameras.)
So, you need a bed or rail, two standards, a bellows, a tripod coupler (usually built into a "bed", and usually a separate piece on a "rail"), a lens board and a lens, and a film back and film holders. A complete 4x5 camera will come with all of these things, as a given (except the film holders).
One of the great things about 4x5 is that there are no such things as your typical "lens mounts", which are brand specific. There are different lens boards for each type of 4x5 cameras, but pretty much any lens can be mounted to pretty much any lens board. All it is is a flat piece of material with a hole in it; no special mounts for each brand of lens.
Each brand of 4x5 camera will need to have its own proprietary back. Though their basic design is the same, and they take the same types of holders and accessories, you can't put the back from one brand of camera onto another brand of camera (except in certain circumstances, such as Sinar/Horseman, or later Toyo/Omega). However, these come with the cameras. The back is a part of the camera itself, and this goes without saying if you get a
complete camera. The back contains the focusing screen AKA ground glass. When using a view camera, you compose the image on the back using the ground glass, with no film in the camera. You then insert the film before you shoot. The film holder moves the glass out of the way and the film ends up where the ground glass was when you were composing and focusing.
I think what you mean by "back" in your third question is actually "holder". Holders are the things that hold film and attach to or are inserted into the back to actually shoot the pix. There are various types of holders. Some hold sheet film. Others hold roll film. Others hold instant prints. Other adapt down to smaller sizes of sheet film. All of these accessories will fit an international standard back, which will likely be present on most 4x5 cameras built in the last 50 years. "Graflok" back is another term used for these types of backs. The type of back on the camera is
certainly a consideration when shopping for a 4x5, especially if you want to use any type of film other than standard 4x5 in. or 9x12 cm. sheet film. In general, you want a camera with a Graflok back. Sheet film holders will fit many (most?) non-Graflok backs back about 100 years, but other types of holders will not.
I would shop for a newer Toyo/Omega or Cambo as a starter camera. They are cheap, full-on systems, will likely be in decent shape, and will allow you to explore all the possibilities a monorail view camera offers. If you just want to shoot some 4x5 with a solid and inexpensive camera with a decent amount of capability without going full bore into a full-on system, I suggest a Graphic View II with a Graflok back. BE CAREFUL. There are three types of Graphic Views, and only one of them (the latest model) always has the Graflok back. To make it simple: If the back has long, exposed leaf springs that span the length of the ground glass, and are mounted permanently in the middle and pinned at each end, it is not a Graflok back. If the back has metal bars that only go about half of the way across the length of the ground glass, and internal coil springs (not visible in most photos), it is a Graflok back. Wish I had pix to show you, but I don't. It is really a very easy distinction to make.
The three models of Graphic View are:
GV: Tilts from the bases of the carrier frames. Spring back, unless converted to Graflok.
Early GV II: Tilts from the middle (top to bottom) of the carrier frames. Spring back, unless custom ordered from the factory or later converted to Graflok.
Late GV II: Same as early GV II, but always has a Graflok back.
There are differences in the lengths of the rails as well (earlier ones are shorter), but be aware that sometimes swaps or modifications have been made.
Check out
www.graflex.org for a better description.