What is the difference between all the Nikon D_ cameras?

What do all the different numbers mean? Like Nikon D40, D90, D3X
>>> What is the difference between all the Nikon D_ cameras?

Lens for Nikon D5100 DSLR?

Nikon D5100 is my first DSLR and it came with the 18-55mm lens. I have compact and bridge camera so the interchangeable lens that you can change is new to me.
Since I do macro photography I was looking to buy a new lens that ranges up to 200mm.
So my main question is:
Can N D5100 use any of the lens produced by Nikon company or do they have to be specific lens produced by the company for that product? And are there other alternative lens for Nikon D5100 so that I may buy cheaper lens for macro photography?
Thank you all for answering.
>>> Lens for Nikon D5100 DSLR?

Which one is better? Nikkor 18-105mm VR or 70-300mm VR?

Priorities
1.Picture quality
2.Built quality(Life)

This is my second lens. Have a 50mm prime
budget is not a problem.
>>> Which one is better? Nikkor 18-105mm VR or 70-300mm VR?

Sony alpha a65 HSS options?

I am trying to find a flash that is capable of high speed sync to work with my alpha dslt..the problem is I want it off camera so the fact that it mounts to sonys proprietary mount is not important to me because I dont want it on the camera..which leads to my question what flash can I use and have it wireless? I have some radio triggers that the tranceiver mounts to the sony and the receiver has a regular hot shoe so can I use a nikon or any third party flash with a hot shoe and hss? Or does some special information need to be sent from camera to flash that would make my sony and third party flash not work together? For example a perfect option would be a flash that shoots hss when triggered regardless of what triggers it wether its the camera or a wireless trigger… also does the wireless trigger sync speed have to do with this? I wouldnt think so…
>>> Sony alpha a65 HSS options?

Computer wont read memory card?

Ok i am using a Nikon d70 with a compact flash memory card. The camera reads the card fine however when i try and transfer the images to pc (via the lead) the pc comes up with format card to continue… i dont want to lose my images so have no idea what to try. Any suggestions?
>>> Computer wont read memory card?

Nikon FG-20 FILM Camera, getting started in photography help?

Alright so I would like to get started in photography, yet my only tool currently is this very old Nikon FG-20 film camera. I would like to a newer DSLR or SLR camera to start and not use film because of its cost and craftsmanship required.

What are my options? I don't know too much about this camera, heres a picture.

http://gyazo.com/a6452acbba66a20186c0b8b547a05a68

Could I sell it for a decent amount in order to purchase a newer camera or is it worth holding onto for future use?

Don't know much about this camera except that its film.

Any help appreciated.
Added (1). Damn =[.Is there any decent starting camera I could purchase as a college student with a part-time job?
Added (2). Affordable*
Added (3). Affordable*
>>> Nikon FG-20 FILM Camera, getting started in photography help?

Dropped Nikon D90, severe damage, help?

So I was at my friend's dorm for a night and we had a bit of a rowdy crowd. I'm not going to explain anything, but my D90, 28-80mm Nikkor (favourite lens: c), and the digital lens that came with the camera (not in the room, can't remember model) all ended up on the floor with several black pieces flaying around, some of which I was unable to find.

Just to clarify, this happened despite the door being locked and secured. Someone found her key and broke in to make out or something, and they knocked everything off the desk.

Anyway, I know both the lenses are pretty damaged. Not the glass, or anything internal (I think), just the little rings that help it stick into the camera. I tested the camera and lenses with the body, and they would take pictures, but then fall out immediately.

HOWEVER, when I was taking the photos, half of the picture would appear black. I was hoping that it was just a coincidence and that both the lenses were damaged in the same way, but I came home and stuck my AF-S 70-300mm in, and the picture remained half black.

This equipment all belongs to my father, and I'm a murdered child if I can't replace everything that's broken immediately. I'd like to get a kind of estimate about repairs/replacements before I sneak around after school to a Future Shop and get a professional opinion. Any advice surrounding the issue would be really appreciated.
>>> Dropped Nikon D90, severe damage, help?

Best lens for shooting video with nikon d5100?

I am interested in buying the nikon d5100 for filming videos, I will also take pictures but they aren't priority. I am thinking of buying the body only so I can get a lens more suitable for filming. I don't want something extremely wide-angled, but also not something extremely zoomed. I dont need anything that can get an entire skyscraper from a short distance. I will be sitting in a chair about 3-6 feet from the camera and want my to be able to see both above the tip of my head and below my collar bones. I hope I specified enough.My price range is quite low, the cheapest lens that fits most of these guidelines will be the one I want. Thank you for any help, I'm quite a newbie.
>>> Best lens for shooting video with nikon d5100?

Which has better picture quality?

This is my first "pro" camera I want it cause my sister has the Nikon D3200 .. But I don't have that much money … I want good pictures just like hers I was wondering if the Nikon D3100 is just as good? If somebody would tell me the goods and bad's of both of these cameras it would help a lot!
>>> Which has better picture quality?

How much are 2gb SD cards for cameras?

I have a Nikon ED 18-55mm camera. Can those are be bought at Walmart?

Thank you!
Added (1). Actually the camera I'm borrowing, but I have to have my own things for. And I'm new to all this investing in memory cards, etc for them.
>>> How much are 2gb SD cards for cameras?