I've been wondering how long it would take for this term to show up here on this forum. I'm actually pretty pleased to see some of the replies as it shows how the folks here actually have quite a bit of discernment and haven't been sucked into the propaganda of what this term is hilariously being used for.
So first, critical race theory emerges from critical legal studies which is meant to apply interpretive methods to the study of the law. Specificially, it was proposed by a scholar named Derrick Bell and adopted by another scholar named Kimberle Crenshaw among a few others as a framework to analyze the different ways US law has been applied on the basis of race. So historically it examined things like housing policies, regional banking practices and criminal justice enforcement and examined the legacy of how race was encoded, for example during Jim Crow, in those laws. It also examined differential legal outcomes on the basis of race.
From here it became applied as a framework to examine other institutions and social practices to look at how race may have played a role in differential outcomes for groups of people. Admittedly, there's been some slippage with the term as some folks use it to applying a race first analysis to any phenomena, but that's a misapplication of the term because it's not about feelings or litigating historical meaning, as a lot of reactionary media and governments lately would like to pretend, but about looking at actual concrete policy.
So why are you hearing about it?
A political commentator and all around grifter by the name of Christopher Rufo proposed about a year ago to make "critical race theory" a buzzword to incite anti-liberal hysteria. Here is one of the tweets where he launched his campaign.
This was the literal launching point of the campaign and these tweets are still up, so this operation happened in plain sight, but it still didn't stop many local school boards, legislatures and governors from going with it full throttle as if somehow this was somehow part of a mass indoctrination campaign.
You've probably heard other variations of critiques against "critical theory" or "cultural marxism" or even hilariously "post-modernism" in terms that make little sense. If you've had the displeasure of hearing of or reading the charlatan James Lindsay, who once appeared on Rogan's show, then you've probably seen these terms bandied about as similar "cultural constructions" to use Rufo's term. It's part of the real culture war being waged by a particular subsector of the right to counter what they claim are a particular subset of the left who embraces what is dubiously called wokeness. In fairness, the "woke" liberals are just as wretched as the culture warrior conservatives, but both often traffic in misapplied theories, half cocked ideals and politics weaponized to gain social capital in media or drive media coverage into contentious discussions for bad faith reasons.
There is truth to the conservative claims that some if not most applications of race first analysis are poisonous, but rather than calling this CRT, a better term is race reductionism, which seeks to mistakenly make race the foundational divide in human existence. At the same time, most of the discourse attacking race based analysis lumps a lot of different political contentions about the effects of racialization and racism together that are wholly unrelated mostly to wage an attack on public goods like public education, for example. The real goal is disinvestment from these public goods and specifically in programs that acknowledge race plays any role at all in some disparities in life. Both liberal and conservative groups use these terms to rally their bases for fundraising, article clicks and occasionally voting. But in actuality ideas like CRT are mostly theoretical abstractions that help describe personal social experience and don't have much use in direct application. If anyone would like further reading, I can give it to you.