Correlation methods for various data variable types

Forgive my ignorance, but I don’t know where I missed this, however when looking at correlations is it true one cannot use continuous and categorical variables as comparables? I assume that it is true, but then does a pearson correlation work only on same variable types (continuous vs continuous ) or is a different method necessary all together (continuous vs categorical)?

Do I have to transform categorical variables in some way to make it comparable?

With that being said, what would you suggest as good material to read to become more proficient on correlations between two variable types?

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