If it helps?
There are lot of options / choices with regards to CCTV, here is my view.
Cameras
The more "lines" a CCTV camera has the better the picture will be, most are around 420 which is acceptable but is not the best quality, better still is 700 / 720 lines and you can also now get 1000 lines. Bear in mind the more lines a camera has the more it will cost. (But the better the picture quality)
The best type of CCTV systems use a camera and “auto iris lens” to allow for light changes, but these are big and as such are expensive, which is where modern electronics has stepped in and you can get cameras with infra red LED’s (For night vision) for less than £15
A thing to consider is the lens, in general the lower the number (Its focal length) the wider angle the camera can see. Being able to see wide may sound good but the wider you can see the smaller things become. So if you want to see for example a persons face a wide angle lens will let you see it, but a narrow angle lens will let you see more detail and so, who it is. You can also get cameras that are “vari-focal” which means you can alter it from wide angle to narrow view.
The majority of cameras used require “shotgun cable” in that they are a cross between a coax and a strait pair. But each end has its own set of plugs to allow for connection to the camera and power supply.
“Modern CCTV” really is a case of plug and play, not even any connections to be made, just a few things to plug together. But this can be a drawback particularly where the power supplies are concerned in that each camera often comes with its own power supply. That’s not too bad until you have 4+ cameras because you need 4+ sockets and space to mount them (Or a 4 way block) I suggest you buy a single plug in power supply and a power lead splitter (It makes life easier, but its your choice)
Pan Tilt & Zoom cameras do exist like you see in the movies, but they all suffer one problem, if you are looking to the left, you can not see what is happening on the right, so although two or 3 fixed cameras may cost more, they are less hassle and look everywhere at the same time. You also need some one to sit watching them in order to move them. (The more professional versions can be set up to “do a tour”)
These are both "eyeball cameras" but the one on the right has a manual varifocal lens, which is why it is bigger.
Monitor
You can use a TV to view the picture but ideally you should have a dedicated TV, even for a home CCTV set up its best to have a dedicated TV.
Not many years ago you had to buy a dedicated CCTV monitor, but now you can buy a relatively cheap TV that will directly accept the output of a DVR. The reason you should have a dedicated TV is that although you can use your (modern) normal TV as the CCTV monitor you can't see anything if you are watching TV. For example you are watching a film on TV and your take away arrives you have to change TV channels to see who is at the door, where as if you have a dedicated TV (Used for the CCTV) you can glance at it and see that some one is coming down your path.
DVR (Digital Video Recorder)
If you have just one camera you don't need a DVR, but modern DVR's also split the final picture so that (for example) you can have 4 cameras showing on 1 monitor. (Some go up to 16)
There are a whole variety of DVRs some can be connected directly to the internet to allow remote viewing of the cameras, some also have an option to plug in a memory stick and copy a part / all of the recorded video, some have a DVD burner, it depends what you want to achieve. (Also how much you want to spend)
The hardest part has to be deciding on the cable runs and actually installing the cables.
Suggestion
I would suggest the best thing for you to do is to buy some CCTV kit and install it on your own house and see how you go
You should also be aware that if you install a camera that can see the public the system it is supposed to be registered with your local council. Also you should have a notice on display saying who is responsible for the system
