The correct answer to this question would be, "It all depends". If you want to protect it from damage while you are walking around, (e.g. as a tourist) you could buy yourself a good camera bag. There are many manufacturers who make reasonable priced bags, like Lowepro, Kata, Crumpler, etc... If you are a serious amatuer with many things in your camera kit, you could look at something more rugged like Pelican cases, or even Lowepro which have HDPE cases. These are designed with a lot of foam padding to protect you camera equipment during transportation etc. For outdoor rugged use, you can look at getting yourself some camera armour (http://www.cameraarmor.com) There are also a lot of manufacturers who make underwater housings for cameras.
A camera case is a case in which one can place their camera in when they are not using the camera to carry and protect the camera.
A soft case will protect a camera from being damaged if it were to fall. It can also protect sensitive lenses from scratches.
There are different things out there that can protect your camera screen. There are actual plastic covers that go on and off easy to protect. Or also you can get other things as well.
There are some camera bags that can protect aganist freezing however this bags are mostly use in the military.
Digital Camera cases, like all camera cases are used to protect and carry the camera while it is not in use.
to protect the lens
The best way to protect your Nikon camera lens is to use a lens cover or lens cap when the camera is not in use. This will help prevent scratches, dust, and other damage to the lens.
The purpose of a camera cover is to protect the camera against outside influences. Outside influences could be rain, temperature, sun and jars. The cover keeps the camera functional.
Some camera cards have a small slider that can be set to protect the card from being written to or erased. Also, some cameras have a function to protect an image from being erased. Check your camera's setup options to see if that feature is available.
There is no briefcase that will do this, although you can get camera cases that are able to protect from this.
You will need to purchase a special waterproof case for your camera to protect it, but yes you can take it underwater. Be warned, without a case, you will probably fry your camera.
A home network camera is a camera that they would have in stores. Home network cameras are basically security or surveillance cameras to protect yourself.