A mage is someone who is highly skilled at casting spells. On Mezia most people know how to cast spells, so calling everyone a mage doesn't make sense. The title is reserved for those who have spent a significant amount of time and effort honing their magic to the point that they are recognized by other mages.
Mages are generally considered to be some of the most powerful people in the world. Mages are often treated with a mix of respect and fear, especially by those unsure of their temperment. A single mage living in a settlement can make it safer from attacks and improve the local quality of life, so many places incentivize mages to live there, such as by offering luxurious accommodations or access to rare items.
Mages approach spellcasting in a variety of ways. Some focus on improving their spells in one or two elements, while others focus on spells with a particular effect. Some like to tinker and enchant objects, while others prefer to focus mana into and through themselves. There are mages who devote their magic to the Ancient Gods, and those who seek to aquire power from the Behemoths. There is no wrong way to be a mage, but some paths may be considered less moral and come with associated disadvantages.
Powerful mages can change the weather and reshape the land, but they are not unstoppable. An arrow to the heart will end the life of even the most powerful mage, and there is no spell to someone back to life.