Selection statements provide a means of executing one of several possible blocks of code. The simplest is the if( ... ) selector. The next most complex is the if( ... ) ... else ... selector.
A similar and related concept is the condition execution operator ?: which is functionally very similar to an if (...) ... else ... selection.
The ECMAScript standard reserves the switch, case and default keywords at edition 2 and mandates that they be supported functionally at edition 3.