SwiftUI onDelete() modifier

I’m trying to learn iOS swift UI development working through some of the Apple tutorials I came across this piece of code. I don’t understand how the onDelete modifier works. This may be more of a swift question than a specific swiftUI question but what’s confusing to me is the call to deleteMovies. The named parameter indexes: is blank. Obviously the parameter is being filled in, but what is the mechanism by which that happens? What is it even called when that happens?

Is there any Apple reference that describes this behavior?

import SwiftUI
import SwiftData


struct MovieList: View {
    @Query(sort: \Movie.title) private var movies: [Movie]
    @Environment(\.modelContext) private var context


    var body: some View {
        NavigationSplitView {
            List {
                ForEach(movies) { movie in
                    NavigationLink(movie.title) {
                        MovieDetail(movie: movie)
                    }
                }
                .onDelete(perform: deleteMovies(indexes:)) <<<—— ???
            }
            .navigationTitle("Movies")
            .toolbar {
                ToolbarItem {
                    Button("Add movie", systemImage: "plus", action: addMovie)
                }
            }
        } detail: {
            Text("Select a movie")
                .navigationTitle("Movie")
                .navigationBarTitleDisplayMode(.inline)
        }
    }


    private func addMovie() {
        context.insert(Movie(title: "New Movie", releaseDate: .now))
    }


    private func deleteMovies(indexes: IndexSet) {
        for index in indexes {
            context.delete(movies[index])
        }
    }
}


#Preview {
    MovieList()
        .modelContainer(SampleData.shared.modelContainer)
}