Voice Activity Detection (VAD), also known as speech activity detection or speech detection, is a technique used in speech processing in which the presence or absence of human speech is detected. The main uses of VAD are in speech coding and speech recognition. It can facilitate speech processing, and can also be used to deactivate some processes during a non-speech section of an audio session: it can avoid unnecessary coding/transmission of silence packets in Voice over Internet Protocol applications, saving on computation and network bandwidth. VAD is an important enabling technology for a variety of speech-based applications. Therefore, various VAD algorithms have been developed that provide varying features and compromises between latency, sensitivity, accuracy, and computational cost. Some VAD algorithms also provide further analysis, for example, whether the speech is voiced, unvoiced, or sustained. Voice activity detection is usually language-independent. This paper discusses various voice activity detection techniques, their results, and their projection towards how they are going through VAD.