l3draw diagram interpretation

I am currently trying to understand the l3draw package defined functions and looked at the example:

dim_new:N l_mypos_dim
draw_begin:
draw_path_moveto:n { 0cm , l_mypos_dim } % Coordinate (0,0) move to 
draw_path_lineto:n { 1cm , l_mypos_dim } % (1,0) horizontally.
dim_set:Nn l_mypos_dim { 1cm }           % Define the new y-coordinate.
draw_path_lineto:n { 1cm , l_mypos_dim } % Draw from (1,0)--(1,1).
draw_path_close:                          % Close path from (1,1)--(0,0).
draw_path_use_clear:n { stroke }
draw_end:

Are the comments the correct interpretation?

My objective is to replicate the answer here: A symbol of a graph of a function without to use TikZ and similar just for fun.