Listitem.Update vs ListItem.SystemUpdate

• SPListItem.Update() is used to update all the values in SharePoint List Item including Modified Date, Modified By, Version fields
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• SPListItem.SystemUpdate() is used to update the values of the list item without modifying the Modified Date, Modified By and Version fields.
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• SPListItem.Update() . Event Receiver is fired in case if listitemupdated,listitemupdating  event is associated. 
• SPListItem.SystemUpdate() Event Receiver won't be fired in case if list item updated, listitemupdating  event is associated