Decyphering a simple regex

Question

The regular expression in question is

(\\d{3,4}[.-]?)+

sample text

707-7019-789

My progress so far

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Answer 1

The brackets remove the functionality of the dot. Brackets mean "Range"/"Character class". Thus you are saying Choose from the list/range/character class .- You aren't saying choose from the list "anything"- (anything is the regular meaning of .)

Answer 2

[.-]?

What this means literally:

character class [.-]

• Match only one out of the following characters: . and - literally.

lazy quantifier ?

• Repeat the last token between 0 and 1 times, as few times as possible.

Answer 3

. in a character group [] is just a literal ., it does not have the special meaning "anything". [.-]? means "a dot or a hyphen or nothing", because the entire group is made optional with the ?.