I think you might do well to read a regex tutorial; there are many, but I like this one in the Java Tutorials. Try the “character classes” section. I think you are correct that the two regexes are equivalent to each other.
Are you implying that the && has no use? Limited use maybe (I have only used it a few of times in over 20 years of using regex) but it does have uses. I can only remember using it in a negative context when wanting to exclude characters from a character set. For example -