The emotional tax is the accumulation of emotions from being on guard to protect oneself from prejudice, from feeling different at work, and the associated effects on health, well-being, and the ability to thrive at work.
Feeling different from the rest of the group and having to be wary of potential prejudices, involve risks to your well-being that accompany this state.
People at the intersections of "race", ethnicity, sex and other aspects of identity are vulnerable to these risks. And when their unique identities and challenges or differences are not addressed, they may feel at risk in the workplace.
We should feel psychologically safe in the workplace. It is this feeling that someone can share what they really think and feel without fear of negative consequences.