Cloud Sprite 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

Flying (This creature can't be blocked except by creatures with flying or reach.) This creature can block only creatures with flying.

How it works : Cloud Sprite

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 Cloud Sprite.

Cloudseeder

Flying {U}, {T}, Discard a card: Create a 1/1 blue Faerie creature token named Cloud Sprite. It has flying and "This token can block only creatures with flying."