A login shell is a shell to which you log in via console or ssh. This is also true if you have not given your username and password due to passwordless login. If you change your user with the su or sux command, this is no login shell. If you log in using the display manager and start a shell, this is no log in shell. If you call bash -login, you are in a login shell (bash), although you did not login at all.
When you start a login shell, login-scripts will be started, and if you start a shell that is not a login shell, other scripts will be started.
What is a login shell
|you enter a computer with ssh, typing username and password||yes|
|you enter a computer with ssh using passwordless login||yes|
|you enter a computer by logging in to the Window Manager, using username and password. Then you open konsole by clicking on it.||no|
|you open a console and type su -, then password||yes|
|you open a console and type bash -||yes|