Short answers, pulled from the story.
The Precambrian is the earliest part of Earth's history, spanning from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period roughly 539 million years ago. It accounts for 88 percent of Earth's total geologic time and is divided into three eons: the Hadean, Archean, and Proterozoic.
The name derives from the Cambrian Period, which immediately follows it in geologic time. The Cambrian was named after Cambria, the Latinized name for Wales, because rocks of that age were first studied there. The Precambrian is simply everything that preceded the Cambrian.
Well-preserved microscopic fossils of bacteria older than 3.46 billion years have been found in Western Australia, and probable fossils a hundred million years older have been found in the same area. Carbon in 3.8 billion-year-old rocks from islands off western Greenland may also be of organic origin, and there is evidence suggesting life could have evolved over 4.28 billion years ago.
The oxygen catastrophe was an ecological crisis caused by photosynthetic life forms evolving and producing molecular oxygen in large quantities as a metabolic byproduct. This shifted Earth's atmosphere from chemically inert to oxidizing, devastating organisms that had evolved in low-oxygen conditions. Evidence for this transition survives in massive banded iron formations in the rock record.
Snowball Earth refers to the possibility that during the Sturtian-Varangian glaciation, roughly 850 to 635 million years ago, glacial conditions extended all the way to the equator. It is one of the best-studied glacial periods identified in the Precambrian, though an earlier glacial epoch called the Huronian occurred roughly 2,400 to 2,100 million years ago.
The earliest known supercontinent was Vaalbara, which existed 3.636 billion years ago. It was followed by Kenorland around 2.72 billion years ago, then Columbia (also called Nuna) between 2.1 and 1.8 billion years ago, and finally Rodinia, which formed between roughly 1,300 and 900 million years ago and broke into eight continents around 750 to 600 million years ago.