system
Given the following post, respond as if you're commenting on Reddit:
human
What does Foucault mean by 'discourse'?
gpt
In short, Foucault's view of discourse mostly centers around the relationship between power and knowledge. His concern wasn't really "what *is* said"/"what is true?" but *"*what *can* we say?" or "which truth is relevant in this context?" Put another way, the question can be phrased as "what is it possible to say/know?" 

The answer to the question is complicated depending on what system you're working in, but Foucault's central argument is that what's possible to say is constrained by relations of power. Power isn't just held by the "powerful"; the key term here is *relation* of power. Power is not a thing you have, but a relationship structured by history, context, politics, ideas, etc. This is the bit that gets Foucault pegged as a radical social constructionist, imo. 

Power and knowledge are intertwined with one another - one follows the other. Power relies on knowledge to function; *however*, power also tends to reproduce knowledges that are best suited for its intentions. (Intentions is a bad word, here - this kind of power is not really held by any one person or even an institution, it's far more diffuse than that. But we'll stick with intentions for now). A good example of this playing out in analysis is his text *Birth of the Clinic*. 

Now, to your specific question: a discourse is a field of various power-knowledges, relations of power, etc that operate via certain exclusions. A discourse is a grouping or network of objects, ideas, places, people, histories that limit *who* can say *what*, *where* they can say it, and *how* they can say it. It's important to understand power and knowledge as distinct concepts so you can understand how they structure various discourses. 

\#metoo is an interesting, albeit politically complex instantiation of this. The relations of power are changing so that people who formerly *could not speak* \- victims of sexual abuse/harassment - now feel as though they *can* speak. But look at *where* they tend to speak - social media, not the justice system. Relations of power are changing for more visibility, but not in every sphere of modern life. Think about all the things that influence how this works - Twitter comes up with a special emoji for it, we have a hashtag for it, but outside the twitterverse we have significant, oppositional legal and political forces, influencing how the movement understands itself internally. 

Another example from politics: we have #BlackLivesMatter. This is a statement that emerges for a variety of reasons, with an extensive backstory, but for simplicity's sake let's say it's a response to disproportionate police killings of black men. 

In response, those opposed to BLM develop statements like All Lives Matter or Blue Lives Matter. A discursive analysis through Foucauldian lens would ask two questions (probably: "How does All Lives Matter *make sense* as a response to BLM, given the history and context of BLM, and how was it *allowed* to make sense as a response in society?" You would have to analyze conservative politics, white supremacy, history, etc to understand how that statement emerged as an intelligible response to BLM. that's a discursive analysis.