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Verses 1-2 suggests that at this point, the universe is still formless, basically not yet formed.
The very first thing God created was light, in contrast to the existing darkness (lack of light).
(Scientists love to point this to the Big Bang, drawing the consistency with our current scientific theories, i.e. light = energy = source of matter as universe cools.) However, God deemed the light "good" in contrast to the darkness. Also, the light can be separated from darkness. Thus we are not just dealing merely with materialistic realm. There is a spiritual dimension already associated with light and darkness. (One of the 10 plagues is total darkness, which strike fear into people).

Note that this light was not from any stars, as they are all later formed.

The first day: evening, then morning: sets the schedule and tone of hope, the sequence of what to expect across the whole bible, that hope and glory comes at the end.

Note that this day is not defined in terms of time, as earth and Sun has not yet been formed, so we cannot say the 24 hour day defined as a full rotation of the earth.