In laymens terms, first there was the big bang. Which created all mass. At the time, this was just basic elements, like hydrogen.
Eventually this mass settled into it's own gravity to create systems. These early systems aren't like our own, rather than being a star surrounded by planets and asteroids, they were simply whirlpools of matter. Over time however, they continued to collapse under their own gravity, until there was enough pressure at the centre of the whirlpool for hydrogen atoms to fuse together, into helium. Which is where the first stars came from. Eventually, these systems burned up their supply of mass creating increasingly heavier elements, and became supernovas (it's important to note, not all of these stars went supernova, a lot first generation stars still exist today, in fact). In doing so, the denser naturally occurring elements were created, such as iron.
Our own system was created from the debris of this first generation of stars (we know this from the presence of these denser elements), formed in a relatively similar way. Planets and Asteroids formed in a similar method to stars (in fact, there even remains some of the dust and gas that made up our planets so long ago in the Oort Clouds [http://en.wikipedia.org/wiki/Oort_Cloud] that surround systems).
Early Earth was very different to how it is today, for starters, the surface it was molten. It was during this time, that another planet (known as Theia) collided with Earth, knocking a large portion of the Earth's liquid crust into orbit. This later formed into what we now know as the Moon. Due to it's much smaller mass, Theia was completely obliterated in this collision.
Eventually the Earth cooled, and life began to develop. There are a lot of different theories about how this happened (some of them even suggest life didn't develop on Earth at all, rather, it originated on Venus, and slowly migrated to planets further from the sun, as they became habitable), I'm not a biologist, so I won't comment on this. But I will say, there's no evidence life was either introduced to or created on Earth by any sort of intelligence.