What is `ViewBuilder` and how does it work?

Answer: @ViewBuilder is a result builder that lets you write multiple views inside a closure and have them composed into a single view. It's what enables the DSL syntax inside body, VStack, HStack, etc.

Code Example:

// SwiftUI uses @ViewBuilder implicitly in most view builders
struct MyCard<Content: View>: View {
    let title: String
    @ViewBuilder let content: () -> Content

    var body: some View {
        VStack(alignment: .leading) {
            Text(title).font(.headline)
            content() // can be any number of views
        }
        .padding()
    }
}

// Usage
MyCard(title: "Summary") {
    Text("Line one")
    Text("Line two")
    Image(systemName: "star")
}