Are there differences between the spirit, soul, mind and heart of a person? What similarities are present? Is it all the same?
It depends on the context which means what. But I would in an explanation divide it like this:
Soul, the life of the person has three "parts" [the soul isn't truly divided]:
(1) Nourishing/growth part, which plants have only and we also have.
(2) The sensitive part (sense as in psychological and otherwise, not just of the body), here we can imagine things, the animals also have this. IIRC this portion can do some natural reasoning in connection to...
(3) The nous/spirit. This is the "highest part" of the soul, the part by which we can know God and purely intellectual things, through which we can receive meaning through something like letters and symbols which goes beyond the natural world. St. John Damascene says: "
the soul does not have the nous as something distinct from itself, but as its purest part, for as the eye is to the body, so is the nous to the soul."
(3) is often in Scripture called the "heart" or the "eyes of the heart" or sometimes even your eyes at all, depending on context. Examples include "
I ask that the eyes of your heart may be enlightened" or "
my ears had heard of You, but now my eyes have seen You [God]" or "
the eye is the lamp of the body. Therefore if your eye is sincere, your whole body will be full of light" or "
blessed are the pure in heart, because they will see God." The word "nous" also means "mind" and is often translated as so, but do know that this is often equivalent to "heart" or "eyes" or "spirit." An example of this in translation (both the faculty working to understand, or perceive, or "see" something spiritual) and it being called mind simply is this in Luke on the road to Emmaus: "
He [Jesus] opened their minds [nous/spirit/heart/eyes] to understand the scriptures."
Another example in the Old Testament is this: "
Then Elisha prayed and said, 'O LORD, please open his eyes that he may see.' So the LORD opened the eyes of the young man, and he saw, and behold, the mountain was full of horses and chariots of fire all around Elisha." With the spiritual eye opened the man could see the Heavenly armies.
The problem with context is some authors will also call (2) the mind. Sometimes "spirit" just refers to your life, like "
into Your hands I commend my spirit" Jesus said, then died. Sometimes "soul" is used for that also. So it really depends on the context, even in the Bible, although it gets easy to recognize and to distinguish.
But there is a difference but they are all "parts" of the soul so-to-speak. Note also, IIRC, (3) is what makes us a true "person." Which is important for it related to the doctrine of the Trinity: God is a Person who loves other Persons eternally. See the first video in my signature. Persons are subjects, "who," that have a nature (the divine nature or human nature or angelic nature) which is a "what." The other animals do not have this part of the soul, just like plants do not have the sensitive part.
When you pray the Psalms note often the language of heart, for it speaks of (3) often, such as in Psalm 50 (51 in Hebrew): "
create a clean heart in me, O God: and renew a right spirit within me..."