How many characters does the "?" symbol typically replace when fine-tuning a selector?

The "?" symbol in selector fine-tuning is used to indicate that the preceding character or group in the expression is optional, meaning that it can either occur once or not at all. Thus, it essentially represents exactly one occurrence of that character or group when it is present, but it makes that character optional. This means that if the character is not present, it accounts for zero characters, but when it is present, it accounts for one.

In terms of how many characters "?" replaces, it can be understood more accurately as representing one character when it appears in the evaluated string. Options that suggest it represents more than one character or zero characters do not accurately describe the function of the "?" symbol in this context. This clear definition allows developers to create flexible selectors that can match a variety of strings while accounting for optionality in the patterns they describe.