»Vagrant vs. Docker
Vagrant is a tool focused on providing a consistent development environment workflow across multiple operating systems. Docker is a container management that can consistently run software as long as a containerization system exists.
Containers are generally more lightweight than virtual machines, so starting and stopping containers is extremely fast. Docker uses the native containerization functionality on macOS, Linux, and Windows.
Currently, Docker lacks support for certain operating systems (such as BSD). If your target deployment is one of these operating systems, Docker will not provide the same production parity as a tool like Vagrant. Vagrant will allow you to run a Windows development environment on Mac or Linux, as well.
For microservice heavy environments, Docker can be attractive because you can easily start a single Docker VM and start many containers above that very quickly. This is a good use case for Docker. Vagrant can do this as well with the Docker provider. A primary benefit for Vagrant is a consistent workflow but there are many cases where a pure-Docker workflow does make sense.
Both Vagrant and Docker have a vast library of community-contributed "images" or "boxes" to choose from.