This is the database component of the stack.
You can interact with it in vagrant commands by targeting it as "db-vm". Eg:
vagrant up db-vm
vagrant ssh db-vm
See vagrantup.com for more details on how vagrant interacts with multi machines.
It gets assigned the IP 192.168.56.2 and a DNS entry makes *.app-vm.codeenigma.com and point to it. You can access it at whatever.app-vm.codeenigma.com directly.
It bundles together: