The talk is about the YAML format and its complexity, despite being deemed simple by some. YAML is used for structured data presentation and competes with formats like JSON and XML. The talk covers various types in YAML, including basic ones like integers and strings and more complex ones like maps and sets. The speaker also discusses some issues with YAML, such as its hidden complexity and the varying support for its features among different tools. The talk concludes by suggesting that JSON may be a better option for those who only require JSON with comments.