Sure, first i'll expand it (short function names to long function names):
;define subroutine sierp
to sierp :n :l
;if the level is zero, stop
if :n=0 [stop]
;Draw 3 lines for the triangle, while calling itself recursively (to draw the triangles on the sides)
repeat 3 [
sierp :n-1 :l/2
forward :l
right 120
]
end
;put the turtle on the right spot
penup
back 100
left 90
back 100
pendown
;Draw a sierpinski triangle, 5 levels deep (200 is the size)
sierp 5 200
That should be clear enough