downto vs. to in VHDL

Question

I'm not sure I understand the difference between 'downto' vs. 'to' in vhdl.

I've seen some online explanations, but I still don't think I understand. Can anyone lay it out for me?

Answer 1

One goes up, one goes down:

-- gives 0, 1, 2, 3:
for i in 0 to 3 loop

-- gives 3, 2, 1, 0:
for i in 3 downto 0 loop