Beside its use in a nice drink called Mojito. Yerba buena have many more uses. Check this info from Webmed.
The leaves are used to make medicine.
Some people take yerba mate by mouth to relieve mental and physical tiredness (fatigue), as well as chronic fatigue syndrome (CFS). It is also taken by mouth for heart-related complaints including heart failure, irregular heartbeat, and low blood pressure.
Some people also take yerba mate by mouth to improve mood and depression; for diabetes; high cholesterol; weak bones (osteoporosis); to relieve headache and joint pains; to treat urinary tract infections (UTIs), and bladder and kidney stones; for weight loss; and as a laxative.
In foods, yerba mate is used to make a tea-like beverage.