What is the difference between legions and mercenaries?

Legions are typically organized military units that are part of a nation's armed forces, often consisting of soldiers who are citizens or conscripts serving under a formal command structure. Mercenaries, on the other hand, are hired soldiers who fight for financial gain rather than loyalty to a nation or cause, often working for private companies or foreign governments. While legions operate under national laws and regulations, mercenaries may operate independently and can be employed in a variety of conflicts worldwide. The motivations and legal frameworks governing their actions differ significantly.