What does expiratory volume mean? is it good to have high volume or low?

FEV1: An expiratory volume is usually how much air your expell from your lungs in a unit of time (fev1 = expiratory volume in 1 second). There are predicted normals (based on sex, height, weight and race). A normal number or a number greater than 70 perent of your predicted normal is ideal.

High: Forced expiratory volume in one second. (fev1). Normals values are adjusted to age and body weight. Higher number better.