The ; semicolon is used for making helpful comments or notes on a line of code. All the characters will turn grey after a semicolon is used. Keep in mind that whenever a semicolon is used at the beginning of the line, this part of the code will not run. We can also place comments to the right of a line of code. For example:

; the procedure below moves the fish forward
to move-fish 
 ask fish [ 
    right random 360 ; we make the fish turn randomly
    forward 1 
 ]  
end

In the model example below, we use ; semicolon to explain two lines of code and the wiggle procedure.