What is a brief description of how the earth was formed?
Here you go.
1) Clumps of matter (e.g.: gas, rocks and some heavy metals) floating around in space decide to start combining after some chance encounter.
Est. 5 b.y.a.
2) A centre is gradually formed within a giant clump of matter. This centre starts "catching" more and more interstellar gas. This centre is called a protostar.
Est. 4.8 b.y.a
3) The protostar gets larger and larger, hotter and hotter until it reaches the point when the gas starts burning. Our Sun is officially formed.
Est. 4.7 b.y.a
4) How about the rocks and heavy metals mentioned at the beginning? They have been orbiting around the Sun for quite a while, so some of them collided and began to form little clumps of matter, also known as protoplanets.
5) After lots of collisions with each other and other intergalactic stuff flying in and out of the newly formed Solar System, one of the protoplanets (which will be Earth) somehow manages to cool down enough for life to begin and the first unicellular organisms begin, evolution blah blah and that's how our Earth was formed.