A soul is the combination of the body and the spirit.
And I, the Lord God, formed man from the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul; Genesis 2:8 IV
The spirit was created before the body, possibly even before the creation.
Nevertheless, all things were before created, but spiritually were they created and made, according to my word. Genesis 2:9 IV
From this we can deduce that the soul is received when the spirit enters the body. Here are references that indicate God considers us individuals while in the womb and the spirit enters the body at conception.
And the children struggled together within her womb; Genesis 25:22 IV
The word "children" is the Hebrew word used for already-born children.
And it came to pass, that when Elizabeth heard the salutation of Mary, the babe leaped in her womb. Luke 1:41 IV
The word "babe" is the Greek word used for already-born children.
Before I formed thee in the belly I knew thee; and before thou camest forth out of the womb I sanctified thee, and I ordained thee a prophet unto the nations. Jeremiah 1:5 IV
Added for clarification:
An easy way of understanding this is to use a house as an analogy. A house is made of walls and a roof. The combination makes a house. You could say that the walls are the body and the roof is the spirit. The combination of the body (walls) and spirit (roof) make a house (soul). body + spirit = soul. Your spirit is what God made to be your identity. Your conscience is the expression of your spirit through your body, the thinking aspect of your soul, therefore limited to what the body is capable of.
Do not make the mistake of believing that any part if you is everlasting. As we know, the body can be broken. The soul can also be broken, by separating the spirit from the body. This happens is death. The spirit can also be destroyed by being cast into the lake of fire, also called the second death.
For those who are having difficulty finding some of the Genesis references, I am using the Inspired Version of the Bible. Note: this translation may or may not correspond with the original Hebrew in places.