.*?any character (except for line terminators), repeated any number of times
\da digit
\.the literal . (4610 / 568 / 2E16)
\da digit
Character Class[A-Za-z]{3} {3}matches exactly 3 characters from the set below:
A-Zone character from A (6510) to Z (9010) (case sensitive)
a-zone character from a (9710) to z (12210) (case sensitive)
\d+a digit, repeated at least once