The phonemic use of clicks is quite rare in languages of the world: they are restricted to languages in southern Africa. Clicks occur in all three groups of Khoisan language families and in the neighbouring Bantu languages which borrowed some of them (Zulu, Khoisan, Swazi, Ndebele). The video adjacent is an X-ray recording of some of the Zulu clicks by a female native speaker who reads a short Zulu sentence 'Iqaqa lega umgwaqo namaqanda ezinkukhu aqhuma athi qhu' (A polecat crosses the road with eggs of chicken and they burst making a qhu sound).
The paralinguistic use of clicks is very common in languages of the world: the dental click is said to express annoyance, concern or regret, while the lateral click is used to persuade horses to start or to accelerate. However, there has also been research which suggests that clicks may serve an organisational function in discourse in that they can be used to mark the transition between one topic of conversation to another (Wright, 2011).
The IPA provides 5 click symbols: labial, dental, alveolar, palate-alveolar and lateral. These symbols specify the anterior release of these sounds. In order to indicate voicing the symbol for the voiced or voiceless velar plosive is added (clicks are essentially double articulations). Nasal clicks are transcribed by adding the symbol for the velar nasal.
Wright, M. (2011). On clicks in English talk-in-interaction. Journal of the International Phonetic Association, 41/2, pp. 207-229.