Terminal, Shell and Console of Linux

What is Terminal?

Terminal Emulator (generally referred as Terminal) basically allows you to access the system through the shell. In general, we can also refer as an application that is used to access the shell of the device.
Default Terminal is gnome terminal for Ubuntu. Other Terminal applications are Terminator, xterm, and so on... 

What is shell?

Shell is a program that takes the input from the user and check whether the syntax executed is correct. If the syntax is correct, it will forward the info to the Linux kernel and from the kernel it will be processed and the output will be displayed.
Default shell for Ubuntu is Bash. Other shell applications besides Bash are C shell, Z shell and so on...

What is console?

Console is a special terminal that starts when no GUI was installed. You start a terminal in a graphical interface, but console in a text-only interface.