Pokémon cards tend to come with numbers at the bottom-right to show you which card it is in the set. For example, you may have a Squirtle card that shows 43/99. This means it’s the 43rd card from a 99-card set.
However, many sets have a Secret Rare card that breaks the set’s total. In our Squirtle example, a card number 100/99 is a Secret Rare card. These cards also often include a holographic star symbol to indicate their rarity.
These cards have an exceptionally low pull rate. As a result, collectors tend to value them highly. Always check the numbering on your card. If you’re lucky, you may have a Secret Rare card hiding among your collection.