The symbol for Mercury has many meanings.
It represents the Greek God Hermes or the Roman God Mercury. Astrologically, it represents the planet Mercury, which is the heavenly power of intellect, communication, and travel.
Alchemically, it represents the element mercury or quicksilver. This element is the union of earth and water, and represents the human spirit.
Some activists also use it as a symbol for third-gender or intersex people, due to Hermes' connection with His child Hermaphroditus, and its potential as a third alternative to the masculine symbol of Mars and the feminine symbol of Venus.
Whatever the reason you wear this symbol, may it grant you abundant blessings.