Signal

 What is signal? Signal is briefly some kind of information that we can carry it through electronic circuits. There are two kind of signals; continuos and discrete signals. Discrete signals are mostly used because digital systems (computer, smart phones etc.) can't use analog, continuous signals. Because they are designed in digital way; only 1's and 0's. So it doesn't show the real information, but if we decrease gaps, we can have good quality enough. For example, when we zoom in a picture in a digital display after a while, depending on how many pixels this photo has, we will start to see one-coloured boxes, pixels. They are coloures with 256 different colours. So that means for example a 5 megapixel camera can divide the image into 5 million pixels, 5 million little boxes that each and every one of them has one and different colour. Human eyes can't see that small so it looks like a clear image to us but in fact, it doesn't really clear. It might get close to continuous signal if we divide it infinity parts but in application we can't. So it is enough to satisfy our eyes.

 Any measurable information which changes through time or space can be a signal. dB of the sound, colours of image, velocity of a car etc.. So signals are represented by functions. Sampling is a method for splitting into pieces and saving a signal. The frequency of sampling determines the quality of signal. Some part will be missing, but so small parts that we can't even see aren't really important. So sampling is important.