The shell is a program that takes commands from the keyboard and gives them to the operating system to perform On most Linux systems a program called bash (which stands for Bourne Again SHell, an enhanced version of the original Unix shell program, sh, written by Steve Bourne) acts as the shell program. Besides bash, there are other shell programs that can be installed in a Linux system. These include: ksh, tcsh and zsh.
It's a program called a terminal emulator. This is a program that opens a window and lets you interact with the shell. There are a bunch of different terminal emulators you can use. Most Linux distributions supply several, such as: gnome-terminal, konsole, xterm, rxvt, kvt, nxterm, and eterm.
LTS is an abbreviation for “Long Term Support”. It is a computer term used to name special versions or editions of software designed to have media for a longer than normal period. It particularly applies to open source software projects such as Linux, especially Debian Ubuntu distributions.