That means covering the mouth is most important because even breathing releases droplets. And the nose should be covered too, but only covering the mouth does help.
This is the same reason the medical authorities have recommended these types of masks for healthcare professionals in areas where N95's are not available. It's better than nothing.
https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/f... (see "HCP use of homemade masks")