In my research of ancient sources, the soul (including all of its faculties) is the true (non-physical) essence of a person (whether he/she knows it or not). In other words, we are our soul. When we say that HaShem created a person, we mean that he (primarily) created a non-physical soul for our created bodies. The accompanying physical body (also created by HaShem) is merely a temporary loaner, designed to allow the soul to express itself in a negative or positive way.

But what is the soul (in terms of function)? The soul is a created (non-physical) connection (bridge) between HaShem and the physical body. When we use terms like "bridge," we are merely using a concept to purvey a close connectedness (i.e.: but not physical closeness) to Hashem.

When Torah says that the soul resides within the body, we understand this to be related (to us) in the language of men. As can be demonstrated, the soul is the bridging interaction (connection) between HaShem and the body. That connection is the essence of a person. In actuality, the soul requires no physical location, space or substance (in and of itself). That being said, it certainly does "interact" with the heart mind, heart and blood.

This G-D given bridge is what makes a person who he/she is. This is WHO the person really (truly) is. However, the soul is a  bi-directional, dynamic situation based upon influence and choice. In other words, our soul extends (ideologically) along two polarities. One leads to righteousness (which strengthens the connection and draws it "closer" to HaShem), while the other CAN lead to wickedness (which is greatly influenced by the body). Although, as is explained below, the soul itself also has influential aspects that can be positive or negative.

Either way, the soul is connected to both of these polarities at the same time. Apparently, HaShem wants us to use this spiritual bridge to be closer to Him (may He be blessed), while our bodies are alive. Some refer to this as the elevation of the body. However, the purpose here is to explain the function of the soul. So we will not explore that here.

Clarification: This essay absolutely refuses to vainly attempt to explain how the soul is connected to HaShem. Besides being an exercise of folly, it leads (and has lead others) to idol worship. Thus, we can and will only concentrate on the definition of the soul itself, and how it relates to the body - based on the sources.