Mac has lost its Dock and menu bar
You can use spotlight (⌘-Space) to do most anything. ⌘⇧A opens Apps folder, ⌘⇧H opens Home folder.
To fix your problem: Try opening the Terminal app (launch via Spotlight). Then type killall Dockand press return. That will attempt to kill the Dock process and relaunch it.
If that doesn't work you can check Activity Monitor (launch via Spotlight) and search for the Dock process to see if it's running at all, and if so, if it's hanging.
cmd-tab will toggle you between applications. use this to get to the finder. once in the finder alt-cmd D will show or hide the dock