Branching Timeline is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Strange new worlds — Reveal the top X cards of your library, where X is the number of differently named lands you control. Put all permanent cards revealed this way onto the battlefield tapped and the rest on the bottom of your library in a random order.