initial-buffer-choice

initial-buffer-choice is a variable defined in `startup.el'.
Its value is

nil

Documentation:
Buffer to show after starting Emacs.
If the value is nil and `inhibit-startup-screen' is nil, show the
startup screen. If the value is a string, switch to a buffer
visiting the file or directory that the string specifies. If the
value is a function, call it with no arguments and switch to the buffer
that it returns. If t, open the `*scratch*' buffer.

If you use `emacsclient' with no target file, then it obeys any
string or function value that this variable has.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 23.1 of Emacs.