The creation of the world happened a little over 6,000 years ago and lasted for 7 days. The creation account is given in Genesis 1 and 2, in the Torah, and is the factually correct account of the origin of the universe and of everything that is in it. The Creation Account is the reason why weeks are 7 days long.
The first day is recorded in Genesis 1:1-5 and records the creation of the "heaven" (KJV) and the Earth, light, and a day-night cycle. The "heaven" or "heavens" refers to the environment that Earth was placed in. This is when day and night itself was created. It is also the reason why the biblical calendar starts each day at sundown on the previous night, because "the evening and the morning were the first day." At this point in time, the Earth is the only physical object in the universe. And it is nothing more than a sphere of pure water. The creation is called "good" by the end of Day 1.
The second day is recorded in Genesis 1:6-8 and records the creation of the "firmament" (expanse). What this expanse refers to is unclear, but is interpreted by some to refer to the Earth's atmosphere. This may also refer to God "stretching-out the heavens" [Psalm 104:2]. The creation is called "good" by the end of Day 2.
The third day is recorded in Genesis 1:9-13 and records the creation of the dry land and the creation of plant life (although the plants are never said to be "alive"). It is made clear that the purpose of the plants was to provide food for creatures that have not yet been created. It is also mentioned three times that these plants reproduce after their kind, refuting any notion that one kind can evolve into another.
God made the dry land out of the water that he created on the first day. The waters "under the heavens" were gathered into one place, called the "seas". This means that all of the dry land was also gathered into one place. Because of the flood, this is no longer the case. The creation is called "good" by the end of Day 3.
The fourth day is recorded in Genesis 1:14-19 and records the creation of the sun, moon, and stars. The "greater light" is the sun, the "lesser light" is the moon, and the "stars" are all of the planets, stars, and galaxies in the universe. The sun takes the place of the light that God created on day 1. The purpose of these sun and moon are as a clock to tell when the days, years, and appointed times are. The creation is called "good" by the end of Day 4.
The fifth day is recorded in Genesis 1:20-23 and records the creation of all of the winged creatures (including winged reptiles) and all of the marine creatures. These creatures are referred to as "swarms", showing how abundant these creatures are supposed to be. This is the first instance where the word "life" is used, and where you find the Hebrew word "nephesh". It is mentioned twice that these creatures were made to reproduce after their kind, refuting any ideas of evolution. The creation is called "good" by the end of Day 5.
The sixth day is recorded in Genesis 1:24-2:1 and in Genesis 2:4-35, and it records the creation of all of the terrestrial animals and of human beings. Five times it says that these creatures were made to reproduce after their kind. Human beings (both male and female) were created in the image and likeness of God, and commanded fill the Earth, and to rule over the Earth and subdue it. God also planted a garden and put mankind in the garden to tend to it and guard it. He gave them permission to eat from any tree in the garden except the tree of the knowledge of good and evil (under penalty of death). At this point in time, both the man and the woman were naked, but were unashamed. At the end of day 6, God called all of his creation "very good", and "finished".
When God created mankind, he created man first, from the dust of the Earth. He created man as a lifeless body that had the potential to live. And when he breathed into this lifeless body, the lifeless body became a "living soul" [Genesis 2:7]. God placed the man (Adam) into the Garden of Eden and had him name all of the creatures. He did this in one day. Later on that same day, God said it was not good for the man to be alone, so he put Adam in a deep sleep and formed a woman (Eve) from Adam's side. This is why the female human is called "woman".
The Sabbath (seventh day) is recorded in Genesis 2:2-3, which properly belongs at the end of Genesis 1. It is here that God institutes the Sabbath and declares the seventh day of every week to be holy. This is why God commanded us to remember the Sabbath, keep it holy, and do no work on the Sabbath [Exodus 20:8-11]. And why it says that the Sabbath was made for man (all mankind) [Mark 2:27]. God had set the example for us to follow.