Telegram is a messaging app that is described as fast, secure, and synced across all devices. It is one of the top 5 most downloaded apps in the world with over 950 million active users. Here's a summary of its key features and characteristics:

• Speed and Reliability: Telegram is noted for its speed, connecting users through a global network of data centers, and is designed to deliver messages using minimal data. It is also described as the most reliable messaging system.
• Cross-Device Functionality: Messages can be accessed from phones, tablets, and computers, with standalone apps that don't require a continuous phone connection.
• Unlimited File Sharing: Users can send media and files of any type and size, with storage in the Telegram cloud.
• Security: Telegram uses a combination of encryption methods including 256-bit symmetric AES, 2048-bit RSA, and Diffie-Hellman secure key exchange. It also offers Secret Chats with end-to-end encryption and self-destructing messages.
• Open Source: Telegram has a fully documented and free API for developers, with open source apps and verifiable builds.
• Group Chats and Bots: The app supports group chats with up to 200,000 members, large file sharing (up to 2 GB each), and the use of bots for specific tasks.
• Customization: Telegram offers photo and video editing tools, animated stickers and emojis, customizable themes, and an open sticker/GIF platform.
• Privacy: Telegram emphasizes user privacy, stating that they do not share data with third parties and allow users to delete messages for both sides. They also claim not to use data for ads. However, one user review notes that privacy settings about who can message you are only available with a premium subscription.
• Data Collection: According to its Google Play Store page, the app may collect data including location and personal info. It also states that data is encrypted in transit and that users can request data deletion.
• Customer service: One user reports being banned after switching phones and states that they were ignored by customer service after using the help button and sending repeated emails. A response to this user's comment from Telegram FZ-LLC indicates that numbers can be unbanned if the ban was a false positive.
• Similar apps: Several similar apps are listed, including Vidogram, Plus Messenger, iMe, VK, X, and Skype.

The app is developed by Telegram FZ-LLC, based in the United Arab Emirates.