This paper presents principles of modulation techniques for modern communication systems along with the corresponding signal detection schemes and prominent receiver structures. Modulation is an integral part of every modern communication systems and provides a means of matching an information-carrying signal to the transmission medium or transmission channel. Modulation techniques are commonly classified into continuous wave (CW) modulation and pulse (PU) modulation. While modulation takes place at the transmitting end of a communication system, an inverse operation called detection needs to be performed at the receiving end. In general, detection aims at recovering the information-bearing signal from the received signal as close as possible in terms of a specified optimization criterion. Digital communications, which usually stands for the digitized representation of originally analogue signals by discrete amplitude and discrete time, is common practice with today’s communication systems. In digital communication systems, discrete information is conveyed between the communicating entities using signal formats from a finite set of waveforms. This allows for the design of very robust transmission systems with the deployed waveforms constructed in such a manner as to facilitate easy information recovery.