Telegram X is the official (yes, you read that right) client spawned by no less than the original Telegram itself; here to offer users a quicker and more fluid browsing experience than its predecessor. Why would the official Telegram app create its own improved, independent clone? Not without good reason, as this newest version is based on the TDLib library which is laying the groundwork for the future of Telegram.
To the naked, untrained eye, any differences between Telegram and Telegram X go unnoticed. Given that Telegram X basically offers a simpler, more streamlined interface for chats while adding in a new tab for making calls to its main screen. From your settings options, you'll also notice that there are several new possibilities when it comes to customizing your interface including a night mode display and bubble-chat box options.
In terms of useable features, Telegram X does exactly what the original Telegram does -- with a few new tricks. Regardless, you'll still get to send text messages, voice messages, send photos, videos and large files, docs, links, GIFs, emojis and a long list of etc, as per usual.
Essentially, Telegram X is an excellent alternative to Telegram which is already a standalone success of an IM app. What 'X' offers is better performance and a wider array of features. In any case, the future of Telegram is now already among us, and it is very promising.