A Set contains your photos and a Collection contains Sets. You would create a Collection for each Event and use Sets for easy categorization. For example, the Collection “Jessie & Ryan's Wedding Day” could contain Sets like "Getting Ready", “Ceremony”, “Reception”, and "Portraits".
Creating a new Collection
To create a new Collection, go to the Collections tab > +New Collection.
Once you've created a Collection, you can upload your photos, and use the +Add Set option to create your Sets for the Collection.