“select” creates a named atom selection from a selection-expression.

select name, selection [, enable [, quiet [, merge [, state [, domain ]]]]]

name = a unique name for the selection

selection = a selection-expression

select chA, chain A 
select ( resn his ) 
select near142, resi 142 around 5 

If a selection-expression with explicit surrounding parethenses is provided as the first argument, then the default selection name is used as the name argument.

delete | cmd.select | commands

Core Commands, Atom Selections, Selection Expressions, Unique Names