bereishit - in [at] the beginning
The meaning of the word bereishit is "at the beginning."
In the opinion of Rabbi Nechemyah (quoted in Midrash Tanchuma at the beginning of Parashat Bereishit), the paragraph tells us that heaven and earth with all their derivatives were created on the first day, none of them having been preceded by any physical matter at all. This fact is attested to by the word bara which describes the creation of "something out of nothing." Rabbi Nechemyah claims that the proof that the whole universe was created already on the first day are the words totze ha'aretz "let the earth bring forth" (Bereishit 1:24)
The word bereishit contains an allusion to the building of the first Beit HaMikdash (Temple) which stood for 410 years, corresponding to the word bezot in the verse "bezot yavo aharon el-hakodesh - equipped with this (410) Aharon will enter the Temple" (VaYikra 16:3). Our Sages have stated (Pesachim 54) that the Temple was created before heaven and earth - the reference is to the plan for the eventual site of the Temple on earth or to its counterpart in heaven. According to Bereishit Rabbah 2 G-d is reported as having envisaged the Temple as being destroyed and being rebuilt, the Torah wrote that word to hint that there would come a time when G-d's Presence would be withdrawn from the Jewish People.
Looking at the words bereishit bara elokim et hashamayim ve'et ha'aretz, it is well known fact that the universe is divided into three basic spheres. One sphere comprises the world of the angels, i.e. celestial regions; the second sphere is what we call "outer space, the sphere of the planetary system; the third sphere is our own terrestrial world. All three parts of the universe were created by the same invisible force.