These frame parameters, meaningful on all kinds of terminals, deal with which buffers have been, or should, be displayed in the frame.
onlymeans this frame is just a minibuffer. If the value is a minibuffer window (in some other frame), the frame uses that minibuffer.
This parameter takes effect when the frame is created. If specified as
nil, Emacs will try to set it to the minibuffer window of
default-minibuffer-frame (see Minibuffers and Frames). For
an existing frame, this parameter can be used exclusively to specify
another minibuffer window. It is not allowed to change it from a
minibuffer window to
t and vice-versa, or from
nil. If the parameter specifies a minibuffer window already,
setting it to
nil has no effect.
other-bufferuses this predicate (from the selected frame) to decide which buffers it should consider, if the predicate is not
nil. It calls the predicate with one argument, a buffer, once for each buffer; if the predicate returns a non-
nilvalue, it considers that buffer.
nil, this frame's window is never split automatically.