The talk was about the Unikraft project, which aims to provide a highly customizable and specialized kernel for applications. Unikraft uses a micro-library approach where everything, including the operating system primitives and language runtimes, are treated as micro-libraries. The project supports two modes of application compatibility, native and binary compatibility. In the native mode, applications are compiled together with the Unikraft build system, while in the binary compatibility mode, applications are built externally and the final binary or image is loaded into Unikraft. The talk also discussed the performance benefits of running Unikraft and showed a demo of running an Nginx web server both natively and in binary compatibility mode.