When your bot receives a message, Telegram sends an update object to your bot. The update contains information about the chat, the user, and of course the message itself. There are numerous other updates, too: https://core.telegram.org/bots/api#update

This object represents one special entity in a text message. For example, hashtags, usernames, URLs, etc.

A function of this type is passed as the second parameter to all middleware. Invoke it to call the downstream middleware and pass on the control flow.

The Bot API supports basic formatting for messages. You can use bold, italic, underlined, strikethrough, and spoiler text, as well as inline links and pre-formatted code in your bots' messages. Telegram clients will render them accordingly. You can use either markdown-style or HTML-style formatting.

API call transformers are functions that can access and modify the method and payload of an API call on the fly. This can be useful if you want to implement rate limiting or other things against the Telegram Bot API.