Telegram is a fast, open-source and secure messenger for mobile and desktop platforms. When you download telegram messenger for Linux, you just get two executables, Telegram and Updater. There is nothing to add these to gnome (or KDE or any other freedesktop.org-compliant desktops) applications list so you can not add this to your favorites or easily launch it with typing its name in gnome shell.

Here’s when desktop files come in handy! Desktop files are standard way to register and application in desktop manager so they can be launched from the applications list, menus and whatever launcher the desktop uses. We build a desktop file for telegram and then put it in /usr/share/applications  or ~/.local/applications. If you put the file in first directory it will be accessible for all users (also you need root privileges to be able to add a file to that directory) but if you put the file in the second one, the file is accessible only for you.

Download telegram logo to be used as an icon for launcher. Create a file named telegtam.desktop with following contents in /usr/share/applications (or ~/.local/applications as mentioned above). You may change ‘Exec’ and ‘Icon’ lines based on your own configurations and directories.

[Desktop Entry]
Version=1.0
Name=Telegram
Exec=/path/to/telegram/executable/Telegram
Icon=/path/to/telegram/logo/t_logo.png
Terminal=false 
Type=Application
Categories=Network;Internet

Learn more about desktop entry files here.
And start using Telegram now!