Telegram is popular chatting app it got 100 million users last month. Since than there are various updates now with the latest Telegram 3.7 Update comes with the public groups, pinned posts, and 5000 member supergroups.
In this update comes with various rights of Supergroups admins i.e they can now also become public. You can share the URL, allowing anyone to join. If someone gets annoying, you can use the admin controls to delete their messages, ban them, mark them as spam, and remove all their messages in the group at once.
The regular groups which reach the 200 user limit can be upgraded to the supergroup by its group admin. The update is rolling out gradually in Europe and America, but are currently not available in several countries in Asia.