iphone camera roll restore

[flimzy]

Hi guys. For quite some time my iPhone has been full to its capacity for storage. But, I can still take snap chats and save them successfully to my camera roll for some reason. I just ignored this and continued to take my photos using snap chat. However, today, after using the snap chat app for a while i tried to take a few consecutive photos and save to camera roll however while saving, it kind of stalled or froze and was stuck saving for a while when finally it saved. This happened for the next 10 or so snaps. Then when i looked in my photo album it had all the screenshots i saved in the last 5 minutes all greyed out and one of them was white with the words .jpeg in it, as well as at the bottom of the camera roll it said Restoring.. I also could no longer save snaps and snap chat stories wouldn't play. After deleting some photos and closing both the album and snap chat apps. I was allowed to save photos after but there was still greyed out photos for some of them. After my phone died and i recharged it, this stopped. What was this? why did it happen randomly after working so many times on full capacity?