Facebook is going to consolidate all of your moments into a single, convenient place that it calls Memories, both on desktop and mobile. This means that you can go back and reflect on all of the memories and such that you've shared with family and friends over the years.
If you use Facebook, then you're likely already familiar with the On This Day feature, which brings up posts, photos, or life events to help remind you of the good or funny times (though it can sometimes backfire). Memories will have a few sections, including On This Day. You'll also be able to see "friendversaries" – an otherwise painful way to say when you and one of your friends connected on Facebook – seasonal and monthly recaps of memories wrapped up nicely in slideshows or videos, and any memory that you might have missed that Facebook thinks you should be aware of.
Facebook says that you can access Memories to the left of your News Feed on desktop or in the "More" section in the mobile apps. Or you can go straight to facebook.com/memories if you want.