In Lightroom you can enter text for an image title or caption. In the example the highlighted thumbnail (#4) has a title "Porsche".
In the next thumbnail (#5) the title is "Trail".
When both of the thumbnails have been selected Lightroom shows the title as "<mixed> because there are two different titles. Now here is the trick - you can add text before or after <mixed> and the text will appear in addition to the wildcard <mixed> text. In this case, since both images were taken in Holland Creek Park, I have appended ", Holland Creek Park".
Here is image 4 only, with the appended text.
And here is image 5 with the appended text.