Breathing is the act of letting a
juice, that is either mixed with alcohol (some vendors use alcohol to mix the flavors together), or have a prefumey/medicinal aroma to them, air out with caps and dripper off for a few hours, usually not more than 12 hours recommended.
Steeping is the act of aging: letting a liquid sit in a cool, dark place to age.
It is always recommended to SHAKE your
eliquid when received, and before you fill your
tank. You might also combine the above options. Shake, breathe, then steep. If the liquid needs it. Not every liquid needs to breathe nor steep. All benefit from the Shake.