The Hadean Period started when the Earth was formed about 4.5 billion years ago. During Hadean times, the Solar System was forming, probably within a large cloud of gas and dust around the sun. The sun was formed within such a cloud of gas and dust. The tendency of matter to clump together finally resulted in the formation of substantial bodies like the planets, and their moons.
The oldest Earth rocks and Moon rocks we know about both date to this time. Water was brought to Earth by comets that crashed into the Earth. This water boiled into steam, because the Earth was still very hot, and formed a steam atmosphere around the Earth. As the Earth cooled down, about 4.3 billion years ago, the steam in the atmosphere also cooled down, and fell as rain on the Earth, and that made the oceans. By 4.2 billion years ago, Earth had land and oceans.