How does the working of HTTP and API key in telegram work?
HTTP : it mainly used in telegram project to make request ie. when the tempreature reches it max value then the ubuntu server make a request to telegram bot to send message to channel and this request betwwen bot and ubuntu server works via HTTP.
API: The Telegram API allows developers to access and integrate the functionality of Telegram with other applications. ie . when you used google map then you can access ola,uber on google map (but these are independent application ) this happen only due to API.
(in another word you are sending message to Telegram Channel via ubuntu server that means accessing the functionality of Telegram with ubuntu sever)