Which theme is this and how to get it on Ubuntu 16.04?

It looks like the screenshot is taken from https://twitter.com/UdaraU3/status/792798140403507200, and a followup tweet at https://twitter.com/UdaraU3/status/796319204513370112 states that it is the Budgie Desktop with the Adapta theme and Paper icons.

From http://www.omgubuntu.co.uk/2016/09/install-budgie-desktop-on-ubuntu, to install the Budgie Desktop, run:

sudo add-apt-repository ppa:budgie-remix/ppa
sudo apt update && sudo apt install budgie-desktop budgie-welcome

The Adapta theme is developed at https://github.com/adapta-project/adapta-gtk-theme. To install the theme, run:

sudo add-apt-repository ppa:tista/adapta
sudo apt-get update
sudo apt-get install adapta-gtk-theme

From https://snwh.org/paper/download, to install the Paper icons, run:

sudo add-apt-repository ppa:snwh/pulp
sudo apt-get update
sudo apt-get install paper-icon-theme

It looks like the PS1 in the terminal is also heavily customized. See @Anwar's answer at https://askubuntu.com/a/816091/15003 for ideas on how to customize the PS1 to fit what is shown in the screenshot.

To set the icons you can use dconf-editor or:

gsettings set com.solus-project.budgie-wm button-layout 'close,minimize,maximize:appmenu'

For the gnome windows (like settings) it's:

gsettings set org.gnome.settings-daemon.plugins.xsettings overrides "{'Gtk/ShellShowsAppMenu': ,'Gtk/DecorationLayout': <'close,maximize,minimize:menu'>}"

close,maximize,minimize:menu would be

menu:minimize,maximize,close

if you want it the other way around. Then, if you did not have it:

sudo apt install gnome-tweak-tool

Start it, set the themes under appearance and enjoy the eye candy :). Thanks for sharing the PPA's!

[edit] I noticed that you can start Budgie Welcome from the start menu. Start it and click default settings. Then you have the option to install the Arc and Material Design themes. It seems the Material Design is the one with the transparency. Click install and then Apply. [/edit]