Difference between collect_set & collect_list

hive (venkat_db)> describe purchases;
OK
salesrepid string
purchaseorderid int
amount int
hive (venkat_db)> select * from purchases;
OK
Daniel 8 160
Daniel 8 160
Jana 9 100
Nadia 10 660
Nadia 10 600
Jana 1 100
Nadia 2 200
Nadia 3 600
Daniel 4 80
Jana 5 120
William 6 170
Daniel 7 140
select salesrepid, collect_set(amount) from purchases group by salesrepid;
Daniel [160,80,140]
Jana [100,120]
Nadia [660,600,200]
William [170]
hive (venkat_db)> select salesrepid, collect_list(amount) from purchases group by salesrepid;
Daniel [160,160,80,140]
Jana [100,100,120]
Nadia [660,600,200,600]
William [170]