The product in use here is manufactured by Proline (whose name you can see on the jar). The company was later known for its commercialization of the lye-based hair relaxer, a process that had already been in use in the African American community for decades. I had difficulty finding information about Proline's earlier products - this appears to be a pomade or softener.

Other than I believe it to be some sort of hair treatment: I have no idea what it actually does. It is also interesting that there was an entire cosmetic industry especially for blacks. To me it's odd that her hair stays braided even though this product is being applied. Yes, what does it do? Great photo by the way.