Laughter contributes to interaction in diverse and vital ways and plays a central role in communication management. Most commonly laughter occurs either at the end of a turn or as a response to a (usually immediately) preceding contribution (see Vettin and Todt 2004). Sometimes laughter is reciprocated by other participants, resulting in Shared laughter (Jefferson 1979). Furthermore, it appears that laughter may also sometimes overlap speech. Interest in the analysis of laughter in discourse has developed mainly from two different streams. First, laughter has been considered in terms of its relationship to humor. Indeed, commonly and canonically, laughter responds to humor. But laughter also routinely occurs within turns in sequences involving primarily non-humorous talk. This resonates with a second stream of interest in laughter as a versatile device in its own right; in particular conversation analysts have investigated how laughter contributes in multiple ways to ongoing courses of social action (Sacks 1992; Jefferson 1979, 1984, 1985; Jefferson, Sacks and Schegloff 1987; Schenkein 1972; Glenn, 2003; Glenn and Holt 2013). This paper addresses the close yet complicated relationship between laughter and humor. Drawing on transcripts, it characterizes the nature (particularly the sounds) of laughs and how they matter to what they are doing. There has been less focus in the pragmatics tradition on the sounds and form of laughter. An exception is an analysis by Tanaka and Campbell (2014), categorizing the sounds of laughter in Japanese into ‘polite’ or ‘mirthful.’ One of the aims of their study is to facilitate machine identification of different types. This paper traces the origins of research in the conversation analytic tradition on laughter’s role in unfolding sequences of action and shows how it allows participants to mark affiliation or stance towards actions and actors. Crucial to such studies is reckoning with laughter’s referent, called the laughable. It proves analytically useful as a starting point to describe actions or features of turn design that contribute to laughter’s relevance. Laughter studies have investigated its workings in informal conversations as well as institutional. In the pragmatics research traditions there is often interest not only in the workings of laughter per se but in how it may help constitute a distinctive activity or sequential environment. This is resonant with a CA conception of talk as context-shaped and context-renewing (Heritage 1984). Laughter regularly occurs in delicate or problematic and in non-serious environments. These two recurrent environments of laughter are not distinct but overlapping. Laughter can contribute towards a transition from serious to non-serious talk, and this makes it extremely useful in environments of potential conflict and disaffiliation. Laughter routinely mitigates meaning or action, marks non-seriousness, helps manage topic and turn transitions, allows participants to navigate towards affiliation or disaffiliation and constitutes interactional intimacy. It is also considered in relationship to the turn in which it is situated and to social variables, as a response, and as appearing in longer sequences. Laughter also adds to identities and this article reviews research considering its role in sequential identity (e.g. as speaker, listener, troubles teller), its institutional role, and identity categories such as place of (geographical) origin and gender. There now is a rich body of pragmatics research on human laughter that has unearthed much about its production, placement, actions, contributions to interaction, and contributions to identities and relationships. Areas that are particularly ripe for further development include: consideration of the relationship between laughter and interactional devices commonly associated with playfulness or non-seriousness; exploration of how laughter contributes to constituting identities and relationships; and analysis of the generalizability/variability of patterns of laughter use across linguistic and cultural settings. Increasingly sophisticated technology for capturing and analyzing laughter will enable fuller analysis of the form laughter takes and its relationship to ongoing interaction.