Google is beginning to roll out the Suggested Sharing feature for Google Photos, but along with it is also coming the Shared Libraries feature, both of which Google initially announced back during Google I/O 2017 in May. Google says that the two new features are rolling out now on Android, iOS, and even the web platform for Google Photos, but it doesn't mention a time frame for the rollout process to be completed so it may take a few days or even the next week before everyone is able to see them and have access to the new sharing tools.
All suggestions for photos and videos to share will appear in the Sharing tab that can be found in the app's navigation bar at the bottom of the UI. This doesn't necessarily mean you'll see any suggestions in the tab, but when they pop up all suggestions will be based on your past sharing habits, so any of the images or videos from Google Photos that you have shared in the past will help to determine future photos and videos that Google suggests you share. All of the suggestions will appear in a carousel of cards separated out in sets of different images based on day, and once you hit the "review" button, you'll be given suggestions of who to share those photos and videos with, and you even have the option to add a personalized message before you hit send.
For Shared Libraries, this feature will show up in the hamburger menu that slides out from the side, and this is aimed at sharing your entire photo library with another person. That said you aren't required to share every single photo and video in the entire library, though you can if you want to, as you'll be given the option to share only specific photos, say from a dedicated folder that you created which contains pictures relevant to the person you're sharing with, and once you initiate sharing that library the recipient will have to accept. The good news is that sharing only really has to be done once and after the other person accepts your shared library request any future photos or videos that are taken will be shared automatically. In addition, the person who receives the shared library can either save all the contents or just save specific stuff.