... are called spread attributes which, as the name implies, allow an expression to be expanded.

 let parts = ['two', 'three']; let numbers = ['one', ...parts, 'four', 'five']; // ["one", "two", "three", "four", "five"]

And in this case (I'm going to simplify it).

 // Just assume we have an object like this: var person= { name: 'Alex', age: 35 }

Is:

 <Modal {...person} title='Modal heading' animation={false} />

is equal to

 <Modal name={person.name} age={person.age} title='Modal heading' animation={false} />

So, in short, it's a neat shortcut, we can say .