Linux 101 stuff. Questions are encouraged, noobs are welcome!

I don't always want to open a terminal as a window in a container layout (tabbed, stacked) but I simply want to open it as a floating window, is it possible to make that for example, pressing $mod+return+space opens the terminal but in floating mode?

It would also be great if, let's say that by default $mod+d opens dmenu, then $mod+d+space opens any program as a floating window, but I don't know if it is possible.