Official Bots are those who have verified badge. These Bots are created and Managed by respective company. Verified Bots will have blue tick next to name (example below).
In this page you will find Best Verified Bots on Telegram. Some of these bots are owned by Telegram and some are created and managed by other companies like Gmail, IFTTT etc.
@design_bot
This bot accept UI layouts and animations intended to improve Telegram. Best contributions are published in @designers.