The Precambrian Era is the very first part of the Earth's history. Its name refers to this era preceding the one that came after it - the Cambrian.
The Precambrian Era began 4.6 billion years ago and ended 541 million years ago, thus encompassing 90% of the planet's history.
Since it happened long ago, there isn't that much evidence of that big period of time. Bacteria fossils that are more than 3 billion years old were found. More complex organisms like algae appeared during Proterozoic eon (the latest part of the Precambrian era).
So weather is basically day to day forecast (rain, sun, clouds) while climate is the all forecasts of an area over years. That’s a simple answer but I hope it helps!