Telegram is a cross-platform cloud-based instant messenger with a focus on security. Use this tag for questions about interacting with Telegram, including use of its official API.
Main features
Messaging
It was the main feature of Telegram. It allows you to send messages to users who have the contacts and we know the nickname.
Groups
The groups are conversations between more than two users, I can reach up to 200 users. Each member of a group can add users, change the name of the group or avatar. Exceeded 200 members, the group becomes a "Supergroup". The supergroup can get to 100,000 users.
Channels
The channels are groups that do not have a limit of users . The peculiarity is that only administrators can write to the channel.
Bots
Telegram Bots are programmed accounts without a phone number. they can not initiate a conversation with a real user. The bot API provides methods to interact with users including sending and editing messages, custom keyboards, commands. (API Documentation)