The Bering Land Bridge was formed about 25,000 years ago, and it remained open for about 12,000 years. During this time, the Amerindians crossed the land bridge and settled in North America. They eventually spread throughout the entire continent, and they became the ancestors of the Native American tribes that live in North America today.
There are other theories about how the Amerindians crossed the Bering Strait, but the Bering Land Bridge theory is the most widely accepted one. It is supported by a number of different evidence, including geological evidence and archaeological evidence.