What was the difference between standing and mercenary armies?

The difference constantly between the army and the mercenary army was in the time frame. That is, the standing army was in constant service and maintenance, and the mercenary army was hired only during the war. In the 16-17 centuries, mercenary armies were popular in Europe, but such troops were also an uncontrollable force, and therefore, they were soon abandoned in favor of regular troops.

One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.