Available Values of context variables in before and after events

 Before insert  ==>Trigger.new.

After insert    ==>Trigger.new,Trigger.newMap.

Before update ==>Trigger.new,Trigger.newMap,Trigger.old,Trigger.oldMap.

After update   ==>Trigger.new,Trigger.newMap,Trigger.old,Trigger.oldMap.

Before delete   ==>Trigger.old,Trigger.oldMap.

After delete     ==>Trigger.old,Trigger.oldMap.

After undelete ==>Trigger.new,Trigger.newMap.