When the turtle draws a square, it does the same thing 4 times.   It moves forward and turns exactly the same amount.   This project shows how to put identical commands into a "repeat" command.

1. The turtle can draw lines that are very thin, very thick, or anywhere in between.
   
   In the square procedure, setpensize 5 tells the turtle to draw thicker lines (5 pixels thick).   Every turtle starts out with a pensize of 1.   You can choose any pensize up to 100.
   
   
2. Repeat 4 means, "Do everything inside the brackets, four times."   Instead of writing:
   fd 100 rt 90
   fd 100 rt 90
   fd 100 rt 90
   fd 100 rt 90
   
   we can write: repeat 4 [fd 100 rt 90]