At an unspecified time, Marisol Vera created a hidden room underneath the Vera Manor. Due to her power of prophecy, Marisol knew that her daughters would become the Charmed Ones. She gave each of her three daughters a gift that would help them for battle. Knowing Mel would be a time witch, Marisol gifted her middle daughter this bracelet that allows her to speed up or slow down her movements through time. This is extremely useful when an opponent cannot be frozen in time.
In The Source Awakens, it was revealed that the bracelet's magic could also be utilised to cast the spell for Balance Restoration. She also used the bracelet to help Harry open the Memory Vault to gain access to the Memory Potion.
The bracelet can only work when Mel activates it consciously by pressing her finger on it, meaning if she is unable to actively press the bracelet, she cannot use its abilities.