Oracle VM VirtualBox Manager
I started using VirtualBox when I was trying to make the transition from Windows based development to a more CLI based approach. Initially I was running VM’s just to get used to Linux servers. Eventually I moved on to Vagrant when I got more serious about SysAdmin work, and since then haven’t used VirtualBox for much other than to glance at the VM’s I have running.
I assume there’s more to learn about VirtualBox but I haven’t come across a need to delve deeper yet.