Stampede 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

Attacking creatures get +1/+0 and gain trample until end of turn.

How it works : Stampede

Original English text — Wizards of the Coast / Scryfall

No additional ruling has been published for this card.

Interactions with other cards

These cards' text mentions Stampede.

Summon: Choco/Mog

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.) I, II, III, IV — Stampede! — Other creatures you control get +1/+0 until end of turn.