Sagrada Familiar 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

Reach, defender Commander spells you cast cost less to cast. Whenever you cast a commander spell, create X 1/1 Stained Glass artifact creature tokens that are all colors, where X is the number of colors of that commander.