Streaming date: refers only to the streaming providers. So it is possible to stream your release e.g. one week later than it is available for sale.
Pre-sale date: thanks to this you can make your release available in the download shops before the actual sales start and collect important sales for the first chart week.
Original Release Date: If you enter a release that is already a bit older, you can enter the original release date here. With the streaming release date you define when the release should be released and with the original release date you make sure that a release which has been released in 2016 for example, is stored with the corresponding date on Spotify and that the order of your releases is correct.