About a year ago, even as the United States was seized by protests against racism, many Americans had never heard the phrase “critical race theory.”

Now, suddenly, the term is everywhere. It makes national and international headlines and is a target for talking heads. Culture wars over critical race theory have turned school boards into battlegrounds, and in higher education, the term has been tangled up in tenure battles. Dozens of United States senators have branded it “activist indoctrination.”

But C.R.T., as it is often abbreviated, is not new. It’s a graduate-level academic framework that encompasses decades of scholarship, which makes it difficult to find a satisfying answer to the basic question:

What, exactly, is critical race theory?

The person widely credited with coining the term is Kimberlé Williams Crenshaw, a law professor at the U.C.L.A. School of Law and Columbia Law School.

Asked for a definition, she first raised a question of her own: Why is this coming up now?

“It’s only prompted interest now that the conservative right wing has claimed it as a subversive set of ideas,” she said, adding that news outlets, including The New York Times, were covering critical race theory because it has been “made the problem by a well-resourced, highly mobilized coalition of forces.”

Some of those critics seem to cast racism as a personal characteristic first and foremost — a problem caused mainly by bigots who practice overt discrimination — and to frame discussions about racism as shaming, accusatory or divisive.

But critical race theorists say they are mainly concerned with institutions and systems.

“The problem is not bad people,” said Mari Matsuda, a law professor at the University of Hawaii who was an early developer of critical race theory. “The problem is a system that reproduces bad outcomes. It is both humane and inclusive to say, ‘We have done things that have hurt all of us, and we need to find a way out.’”