If you want to download and back up all those pictures on Google Photos over the years, try using Google Takeout. It's a lot faster than backing up manually, especially for people with huge batches. Google Takeout allows you to see the data you've given to Google in other areas too, like Google+ (rest in peace).
Rob uses Google Photos to back up his phone's photos. He wants to get those Google Photos pics onto a hard drive. Leo recommends Google Takeout, which allows users to download data from their Google features (including Photos). It allows users to download in a variety of formats and helps to avoid disaster if they get locked out of their account.