Faceted application of subject terminology means breaking down a subject into different parts, like how a toy can be broken down into different pieces. These different parts are called "facets." Just like how a toy has different facets like its color, shape, size and material, a subject can have different facets too.
For example, if we're talking about a book, some of the facets we can look at are the author, the title, the genre or the topic. Each facet helps us understand the book better, just like how each piece of a toy helps us build the toy.
In libraries, people use faceted application of subject terminology to organize books and other resources so that they can be easily found by people who are looking for them. By breaking down the different facets of a subject, it becomes easier to search for information on a specific aspect of that subject. Imagine trying to find a toy without knowing which box it's in, but when you know the different parts of the toy, you can find it more easily.
So basically, faceted application of subject terminology is a way to organize information and make it easier to find by breaking it down into different parts or facets, like how a toy can be broken down into its different pieces.