So that is what signals are all about. Well, they are one of the many tools for doing these things mentioned above. CD players have nothing to do with wavelets, either. Those types of signals are never subjected to these kinds of signal processing. Well, I'll give you an example of the type of signal processing I'm talking about.
Submarines know what's going on under the sea through the use of sonar.
Now, a submarine will look for other submarines via this process of sending out sounds and listening for reflections. Of course, there is no way of telling directly what the sound is being reflected off of. In particular, whales will reflect sounds just as well as a submarine, in fact in a very similar way since they are about the same size and shape. So, when the sonar man listens to the reflection, there is really no way for him to distinguish between the two, because his ears aren't that sensitive. However, there are differences that can be detected by analyzing the signal in a way I mentioned above.