I just want to bring out one point, but there are literally thousands of ideas written about this one phrase.
In the beginning of... It's deliberately open ended. The Vilna Goan says that by uttering the word בראשית, G-d created time. We usually think of time as a link or continuation of past and future. There was something, and then... something else. But its no secret that this idea of time is a paradox (as in Zeno's paradox). A new moment in time is gone as soon as it has come. Identifying where this thing called time is is impossible. We just observe that things change, move, and call this phenomenon time.
The Vilna Gaon revealed something to us, if will listen. The word for time in hebrew, זמן, also means preparation, זימון. If time is created with a word that means, among other things, "in the beginning of", that means time is... anticipation, hope. Time is not just change, it is direction and growth. The world was formed out of an unidentifiable substance which is in essence, the ability to grow, and to actualize potential. The word for G-d in the verse is אלוהים which is the expression of the creator that limits for us or focuses G-d's infiniteness and creates a power structure. But before that expression, time was created, the ability to harness the infinite potential within any structure. The word for hope, תקוה comes from the word for direction, קו. It means coming from a feeling of constriction and chaos and then reaching inside and finding a yearning. Feeling limited externally, but knowing internally that there are no limits and there is salvation.
The very first words of the Torah, בראשית ברה אלוהים, sings out, that the essence of creation ex-nihilo is transforming physicality, limitations, constriction, into infinity, and it reveals how this infinity is at the root of everything from the very begining.