Question:
What is a ghost? Is it a soul that didn’t go up or down?

Answer:
A ghost is another word for “spirit.” God is a Spirit, and the third Person of the Godhead is the Holy Ghost or the Holy Spirit. God made man with not only a body and a soul like the animals, but he made him in God’s own image so man also has a spirit (Genesis 1:27).

Regarding the second part of the question: Human souls or spirits do not wander but go to a definite place when their bodies die. When a person’s body dies his soul and spirit either go to be “with Christ” in “paradise” (Philippians 1:23; Luke 23:43), or to “the place of torment” (Luke 16:28).