Select

Select[data,crit] picks out all elements ei of data for which crit[ei] is True. 

Select[data,crit->prop] returns the property prop of the selected elements.

Select[data,crit,n] picks out the first n elements for which crit[ei] is True. 

Select[crit] represents an operator form of Select that can be applied to an expression. 

Please visit the official Wolfram Language Reference for more details and examples on core symbols.