How to understand the ingredient of this sentence？

Maybe my computer science background can help - I don't have any experience working with transformers but this verbiage is similar to my trade.

To me this feels like it's missing a word and wasn't proofread for clarity. I would assume it should be rephrased as follows:

The input to this transformer should be an array-like series of integers or strings, denoting that represent the values taken on by of categorical (discrete) features

I do not know exactly what these "categorical features" are, but the use of "discrete" implies that they are unique. My best guess is that the array-like input maps to an analogous array of categories, and each entry controls a particular feature.