for (variable : list_or_set) {
code_block
}
When executing this type of for loop, the Apex runtime engine assigns variable to each element in list_or_set, and runs the code_block for each value.
Integer[] myInts = new Integer[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; for (Integer i : myInts) { System.debug(i); }