The answer is found in several places in Scripture.
SHORT ANSWER:
Soul is the combination of spirit and flesh(body).
1) James 2:26
"For as the body without the spirit is dead, so faith without works is dead also."
2) Genesis - God breathed (his spirit) into the flesh and it became alive.
The term 'soul' is also referred to as a 'living being' or creature.
Genesis 2:7 "And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul."
3) The Bible also mentions a person's 'heart' or unseen center or core. My studies show is our true invisible self.
Proverbs 4:23 "Keep your heart with all vigilance, for from it flow the springs of life."
WE ARE A TRINITY
Genesis 1:26 "And God said, Let us make man in our image, after our likeness..."
1) Our Invisible True Self [HEART/CENTER/CORE] Is in control of all.
God the Father is the True Self of God.
2) Our Unseen Spirit (connects #1 and #3)
Like God's Holy Spirit, our spirit only communicates to our body the will, emotions, and desires of our Invisible True Self.
John 16:13 "But when He, the Spirit of truth, comes, He will guide you into all the truth; for He will not speak on His own initiative, but whatever He hears, He will speak; and He will disclose to you what is to come."
3) Our Physical Body
Just like Jesus (Y'shua) is the physical expression, reflection, or manifestation of God,
Our Body is an expression of our Invisible True Self.
Romans 10:9-10 "... if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved."
Psalms 51:10 "Create in me a clean heart, O God, and renew a right spirit within me."
Proverbs 3:5 "Trust in the LORD with all your heart, and do not lean on your own understanding."