Docker is a tool that allows developers to package applications into containers that can run on any infrastructure. It provides a way to separate applications from the underlying infrastructure so that they can be easily deployed and scaled. Docker uses images as templates for creating containers which contain everything needed to run an application. Containers allow for more efficient use of resources and easier distribution of applications between development and production environments. The presentation provides an overview of Docker and demonstrates some common use cases for developers, such as building images, running continuous integration tests, and facilitating continuous delivery of applications.