In "More Metacharacters", third explanation page, what is that "(-)" doing there?

Question

In "More Metacharacters", third explanation page, what is that "(-)" doing there?

The specific lesson is about the question mark metacharacter, but there's a "(-)" in the string that really got me confused.

The metacharacter ? means "zero or one repetitions".

Example:
import re

pattern = r"ice(-)?cream"

if re.match(pattern, "ice-cream"):
print("Match 1")

if re.match(pattern, "icecream"):
print("Match 2")

if re.match(pattern, "sausages"):
print("Match 3")

if re.match(pattern, "ice--ice"):
print("Match 4")

Answer 1

"Causes the resulting RE to match 0 or 1 repetitions of the preceding RE. ab? will match either 'a' or 'ab'."

https://docs.python.org/3/library/re.html#index-5

Answer 2

Thanks, Diego!

And here is an online RegEx tester that I found very useful: https://regex101.com/

All the best!