The ? (question mark) wildcard means exactly one arbitrary character. Note that it does not work when trying to find non-UTF-8 or multibyte characters. If you want to search for these characters, the expression ?? might work, or you can use the * wildcard instead.

Search expression example?
Matches

example1

examples

Does not match

example.com

example12

query-by-example

example?

Search expression ?example?
Matches

1example2

Does not match

example.com

example12

query-by-example

Search expression example??
Matches

example12

Does not match

example.com

example1

query-by-example