A correspondence is sort of like a list of meanings or associations with objects, colors, etc., specifically in this case with magical usage.
Correspondences are the energies and actions attributed to a certain magical item, like herbs or crystals. There's no need to be sorry, we've all been there before!
They are associations. Each herb, crystal, oil, etc is believed to have specific associations also known as "correspondences". These allow us to work with items to suit our desired outcome, such as love, money, divination, etc.