It is important to note both aromas and flavors — as the two are closely linked — though the nose is far more acute than the tongue at detecting what it is you are consuming when you taste wines.
The tongue detects four primary flavors: sweet, salt, bitter, and sour. Every flavor you experience can be derived down to a combination of those four components.
The nose, on the other hand, is capable of detecting several thousand separate types of scents, so it is able to identify much finer variations in aromas.
After tasting multiple wines in one setting, your tongue may become fatigued. This can make it extremely difficult to identify the flavors of a wine. The nose, on the other hand, seems capable of lasting much longer than the tongue. Therefore, when tasting wines, not only is the nose relied upon more for its acuteness, but also its endurance.