In #tmux, a "horizontal split" pane window places the panes side-by-side via "Ctrl+b %" or ":split-window -h".

In #Vim, it's a "vertical split" by executing either "Ctrl+w Ctrl+v" or ":vsplit".

No wonder I'm always confused.

Is it a horizontal split because the windows/panes or horizontally placed, or a vertical split because there is a vertical line separating the windows/panes?

#Linux

@atoponce i think vim is wrong about this.

i have the tmux splits mapped to "-" and "|", so i don't have to think about that.

and because i use tmux, i rarely need or want vim's :vsplit. i almost always use :split.