This new feature permits the pictures selection in Smart Collection based on Event IPTC/xmp metadata.
Event, like People, Location, Date, Copyright are very important information to manage picture. This helps to find back the picture of a wedding, an art-exhibition, anniversary,....
In the past, people used folders structure to do this. Later, they used keuwords.
But now, with so many pictures, keywords lists are very, very long. So, we lost many time to find the right keyword.
And computer can't understand keywords.
The Event information exists in IPTC extension but LRc don't use (yet ?) IPTC extension in the smart collection. So, uses it, please.
Today, metadata are very important because it's human/machine usable. So, as a photographer, user can exchange information between application (like LRc, Photoshop,..), user <-> media (like social media), user <--> Customer,....