Genesis 1:1 "In the beginning" - what does this really mean?
The Bible seems to say in Col 1:18 that Jesus is the beginning: "And he is the head of the body, the church:
who is the beginning, the firstborn from the dead; that in all
things he might have the preeminence. "
That, to me, seems to answer the question you ask about what the beginning really means. To me, it seems to mean Christ, who is the firstborn from the dead.
Perhaps one way to think of it is that Jesus was first born from the dead so that he could create believers. Believers would be the heaven and the earth part.
The heaven and the earth are both interesting words to define as well. When we see that God created the heaven and the earth, we might possibly use Col 1:18 to substitute the word 'Jesus' with 'the beginning' and get something like: In Jesus, God created the heaven and the earth. I am not advocating changing the scripture but only to show how its meaning might be. Similarly, when we see the word 'heaven', we might get at the meaning of that word by thinking of the true believers with Jesus. The true believers seem to be called 'heaven' in Matthew 24: "gather together his elect from the four winds, from one end of heaven to the other "
By substituting for meaning, we might possibly get something like: In Jesus, God created the true believers and the earth.
That still leaves the term 'earth' to define. The Bible tells us that the dry land is called earth (Gen 1:10). Jesus was in a dry place, if you will, on the cross. We see that Joseph, a picture of Jesus, was rejected by his brothers and thrown in a pit, where no water is (Gen 37:24). This was a metaphorical picture of the cross experience. So, to me, the term 'earth' is speaking of the cross experience, both for Christ and for those who bear their cross, if you will, for the sake of Christ.
So, to me, Genesis 1:1 might be thought of as something like: In Christ, God created the true believers with Christ and the cross that they bear for his sake.
Something akin to, in my view, "For to me to live
is Christ, and to die
is gain. " In this case, the phrase 'to live is Christ' being the cross to bear part, and 'to die is gain' being the believers with God part.