This is the language that is shipped with the Lego RCX. It is designed to be familiar feeling to new programmers who are more comfortable with the real physical Lego bricks - and so tries to emulate their simplicity in the code.
It is very easy to use, very colourful, and is probably the best introduction for very new users. The introductions, and the Mindstorms constructopedia will get them up to speed with very basics of robot control and feedback. Even for some of those with experience programming desktops, programming robots can sometimes be a little different and this is a gentle introduction before trying to get the alternatives like Mindscript, NQC, Lejos or BrickOS running.
There are no variables, and the use of subroutines is very, very simple - with no concept of parameters. You cannot do complex manipulation of the motor, sensor or IR ports. You cannot store or log data.