Regular expression \p{L} and \p{N}
\p{L}matches a single code point in the category "letter".\p{N}matches any kind of numeric character in any script.
Source: regular-expressions.info
If you're going to work with regular expressions a lot, I'd suggest bookmarking that site, it's very useful.
These are Unicode property shortcuts (\p{L} for Unicode letters, \p{N} for Unicode digits). They are supported by .NET, Perl, Java, PCRE, XML, XPath, JGSoft, Ruby (1.9 and higher) and PHP (since 5.1.0)
At any rate, that's a very strange regex. You should not be using alternation when a character class would suffice:
[\p{L}\p{N}_.-]*