LXTerminal is the LXDE version of a terminal emulator that you will use when prompted to launch the terminal or use the command line (CLI). General information and basic commands for the terminal are available at Using the Terminal.
Launching the terminal
Click on the Main Menu icon in the panel and select Accessories and then LXTerminal. Although in Lubuntu 15.04 and later lxterminal is located in the main menu under System Tools and then LXTerminal. There also is a keyboard shortcut of Control+ alt+ t.
If you would like to customise how LXTerminal appears. head over to customising LXTerminal