“Universal” prepaid debit cards are also known as “network branded” or “open loop” prepaid debit cards. These are cards that are accepted at most merchants. The cards are typically branded with the Visa, MasterCard, American Express, or Discover brands which allows them to be used at any merchant location which accepts those brands. These prepaid debit cards are “universal” to the extent that they can be used at any location accepting the brand.
Some gift card and prepaid cards are not network branded (instead, they are “closed loop” or private cards) which do not enjoy universal acceptance.