Ephedra is a stimulant. It stimulates the brain, increases your heart rate, constricts your blood vessels, which makes your blood pressure go up, increases your metabolism, and allows you to breathe a bit easier since it expands your bronchial tubes.
It's considered a 'performance enhancing drug', but there isn't much proof it significantly improves athletic performance. Since it increases body heat, it can be used for weight loss, but I wouldn't recommend it.
The sides aren't pretty either. Your skin can react pretty badly to it. It can make you nervous and dizzy. Other sides are insomnia, vomiting, heart attacks, strokes, seizures, and it can even kill you.
Hope this helps.