This presentation discusses building domain-specific languages (DSLs) in Groovy. It defines DSLs as languages targeted at particular problems with syntax focused on the domain. The presentation provides examples of DSLs implemented in Groovy, including Gant which is an Ant build tool without XML. It discusses Groovy features like closures, delegates, dynamic methods, and ExpandoMetaClass that are useful for building DSLs. The speaker advocates that Groovy is well-suited for implementing DSLs on the JVM due to its dynamic and meta-programming capabilities.