Time travel explained

I have never been a big fan of Time Travel, but that doesn’t stop me from watching movies/series related to it, like Back to the Future, Game of Thrones (latest TV season, not the book) etc. I found this YouTube video from Vox interesting. Did I understand it fully? Nope. But I did understand it to some extent to figure out that I cannot go back and kill my grandparent and also as to why Bran Stark (Spoiler here) couldn’t have changed what had happened. For fans of Game of Thrones: There will be spoilers in this video, so if you haven’t watched the latest season (all episodes) then don’t watch this video, unless you love seeing spoilers.