This talk was recorded at Scala Days New York, 2016. Follow along on Twitter @scaladays and on the website for more information http://scaladays.org/. Abstract: Pattern Matching is a great and very popular feature in Scala - yet many are quite unsure about how it works exactly. What can I match on? How efficient is it? What do case classes have to do with it? What's an extractor? What's the deal with unapply and unapplySeq? And what exactly is the role of "::" or "+:" when matching sequences? If I build my own extractors, what exactly goes in, what comes out? This is an entry level talk for developers who'd like to look "under the hood" of pattern matching, and who haven't written their own extractors yet.