100% Vegan theoretically means that a product contains no animal products, such as meat or eggs, and no animal-derived ingredients, like gelatin. This claim, however, is not regulated, so producers and manufacturers are free to judge for themselves if their product is 100% vegan of not.
Processed foods may contain animal products or animal-derived ingredients listed under names that seem vegan to the untrained eye. For example, carmine, a food additive, is often made by boiling insects.
Even if a product does not contain animal ingredients, they may have been used in the manufacturing of the product: the charcoal used to filter or process foods like beer and sugar sometimes comes from an animal source.
This claim can be found on baby food, beverages, and bread.