What is the playoff format for the American and national league division and the World Series?

As you know there can be 4 teams in the Playoffs, the 6 Division Winners and the 2 Wild Card winners from both the American and National Leagues.

The team with the best record in either division will play the Wild Card winner for their league but if their Wild Card winner is in the same division as them then they'll play against the team in their same league who has the 2nd best record.

How it determines who holds home field advantage for the Division Series and the League Championship Series is based on their Regular Season record but this only applies to the Divisional Winners, Wild Card winners can never have home field advantage during the Divisional Series or the League Championship Series.

The World Series' home field advantage is as you know based on the outcome of the All Star Baseball game.