winrar functions, what do they do

There are some function of winrar that I don't know what they do. 1) change drive(complete no idea what it does) 2) virus scan (it has a in-built scanner? Or it use your anti virus?) 3) self extract: if you double click a rar archive and click the self extract what does it do? Extract itself where? 4) extract whithout confirmation means it will extract itself without you knowing?