Select[list, crit] picks out all elements of list for which crit[] is True.
Select[list, crit, n] picks out the first n elements for which crit[] is True.
Example: Select[1,4,2,7,6, EvenQ]. The object list can have any head, not necessarily List. See The Mathematica Book on the web: Section 2.2.7. See also: Cases, Take, Drop.
Select[list, crit] picks out all elements 
of list for which crit[
] is True. 
] is True. 
1,4,2,7,6
, EvenQ]
. 