See also the official documentation:
Help Center > Members Manual > Working with photos > Viewing photos
Execute a photo search by placing a word or string in the box at upper right and clicking on the Search button.
The search will search all photos over all the Photo albums in your group. It does not search the Files area, nor does it search the Emailed Photos folder.
The search does partial word ["string"] matches on photo and folder names, but not on other fields.
If the match is with an album title or description, all photos in that album will be returned.
Search results are displayed in case-sensitive alphanumeric order...that is, "Z" comes before "a".