codec comes in different capabilities. a profile is a collection of techniques used in a codec engine. the more sophisticated techniques are used, the higher compression efficiency, and the better codec profile with different bit rate. in H.264, typically base profile is used in lower cost codec engines, and main profile or high profile is used for more high end IP cameras.
IP camera can compress video images in more than one codec, such as H.264 and MJPEG.
IP camera provides multiple video streams, probably, in multiple video profile.
IP video stream that NVR can subscribe to do live watching or recording
Codec specification of the video: resolution, ips(image per second) and bit rate.
Lens format is the focal plane size of the lens. You can use 1/2" format lens for smaller image sensors, such as 1/2.7" or 1/3" or 1/4", but not the other way around. Or else, you will end up seeing part of the lens barrel shadows at the corners of the image especially in wide angle mode.
Mega pixel lens / Lens resolution
Optics play a very important role in cameras. And good lenses are critical to build a good surveillance system. When we talk about resolutions, we often talk about image sensor resolutions but not the one for the lenses. Your image is going to be only as good and sharp as the capability of the lens that you use in your camera. Mega pixel lenses can "resolve" mega pixel resolutions on its focal plane.
Infrared LEDs are used to illuminate low light scenes. Typically they are 850nm (visible to most human), and non visible 920nm.
Digital Day and Night
Instead of ICR, it uses a IR pass filter which passes the visible spectrum of lights as well. It works great in artificial light conditions, such as indoor applications, but when you have light sources that emits IR spectrum, such as incandescent light blurs, halogen or sun light, the color can be slightly distorted.
ICR (Infrared Cut-filter Removal)
Infrared Cut-filter Removal is a mechanism used in True Day and Night cameras. Camera sensors are sensitive to a wider spectrum of lights the spectrum of visible lights. So it can see what you can not see. During the day time, it puts the IR cut filter between the lens and the image sensor in True Day and Night cameras. Without this filter, the sensors will see the non visible lights, and may distort the colors on the scene or blur the scene. Also, Frequently Infrared LED lighting is used to assist to low light conditions. So the IR cut filter is removed during the night time so that the IR LED light source can be used to sense the scene in IR spectrum. Because human eyes can not see the IR, the scene is rendered in black and white.