Chr(10) is the Line Feed character and Chr(13) is the Carriage Return character.
You probably won't notice a difference if you use only one or the other, but you might find yourself in a situation where the output doesn't show properly with only one or the other. So it's safer to include both.
Historically, Line Feed would move down a line but not return to column 1:
This
is
a
test.
Similarly Carriage Return would return to column 1 but not move down a line:
This
is
a
test.
Paste this into a text editor and then choose to "show all characters", and you'll see both characters present at the end of each line. Better safe than sorry.