What is named by $ICBN$?

$A$ species is defined as "the group of actually or potentially inter-breeding natural populations producing fertile offspring and reproductively isolated from such other groups". The above statement is given by

Karyotaxonomy is the modern branch of classification which is based on:

How many names are provided in the binomial nomenclature of an organism?

Into how many groups did Theophrastus classify plants?

The name $Rauwolfia$ was given by whom?