There are plenty of popular messengers available for Android, and it's a tough market considering the fact that people prefer to use one or two of them for their daily communication. WhatsApp is considered to be the leader in this branch, but there are plenty of alternatives.
Telegram is sort of new in the market, being there for five years and gaining more than 200 million users. For reference, WhatsApp has more than 1.5 billion users and Viber (most popular in Eastern and Southeast Europe) has more than 1 billion users.
Telegram manages to offer a pure instant messaging app without much glamour on the side, but it definitely behaves faster than the modern Messenger app, for reference. Its design resembles WhatsApp and Viber, but other than that there is not much to say about it.
There are some things it offers which have delighted us. You can easily send media and files without any limits on their type or the size, meaning you can easily share larger files which the other messaging apps might reject.
Also, group chats can hold up to 200,000 members, meaning it may be perfect for projects which require many people sharing large files (like an IT project). You can also edit the messages you sent, have the messages self-destruct, control if the photos are stored on your device, etc.
It can boast about its encryption as well, as it uses a combination of 256-bit symmetric AES encryption, 2048-bit RSA encryption and Diffie-Hellman secure key exchange. However, messages are not encrypted by default and you will have to create a New Secret Chat in order to force encryption. This is not that great, as people don't want to think about it too much.
• It's fast and simple
• Easy sharing of large files
• Groups of up to 200,000 members
• Sent messages can be edited
• You have to manually enable the encryption of your chats
• It's just not popular enough to replace other messaging apps