\ban ASCII word boundary
\d{3}a digit, repeated exactly 3 times
\ban ASCII word boundary
\s*any whitespace character, repeated any number of times
.*?any character (except for line terminators), repeated any number of times
\s*any whitespace character, repeated any number of times
Adónem számlaszáma: the literal text Adónem számlaszáma: (case sensitive) \S*any non-whitespace character, repeated any number of times
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string