It's just normal VAT, the issue is that many "necessary" products don't have VAT on them, but tampons or pads do, even though they are a biological necessity.
It's like women-day-off when they're on their period. On one hand, it'd be nice and makes sense. On the other hand, that sex-based discrimination.
Meanwhile over there we got flat VAT for everything. No tampon tax issues! :) Paying extra 21% for basic food sucks though.
Also, if we're talking about less common alternatives, women can use menstrual cups instead of tampons and pads.
It's just normal VAT, the issue is that many "necessary" products don't have VAT on them, but tampons or pads do, even though they are a biological necessity.