What exactly is "identity politics" within a leftist theoretical framework?

Out of all the buzzwords online and in the culture wars, I understand "identity politics" the least. I know it has a basis in theory but it seems like every individual person has their own definition of what it means. Chuds use it basically interchangeably with "woke", libs use it as a cudgel against marginalized groups who call them out on their moderate-fascist bullshit, and for a while I was under the impression that it was a nonsense term only used by our enemies.

But I see leftists here and in the wild using the term and I lack a theoretical understanding of its meaning and what phenomenon exactly it's describing.