React syntax question for React.ComponentProps

Let's break this down.

First typeof - typeof infers a type from a constant.

So for example

const foo = {
 a: "hello", 
 b: 999
}; 

type TypeofFoo = typeof foo; 

//type TypeofFoo = {
//    a: string;
//    b: number;
//}

So for typeof a React component:

const MyComponent = (props: {
    name: string
}) => {
    const {name} = props; 
    return <div>{name}</div>
}

type  TypeofMyComponent = typeof MyComponent; 
//type TypeofMyComponent = (props: {
//    name: string;
//}) => JSX.Element

We can see the the typeof a React component in this case is just a function with a particular signature and returns a JSX.Element.

Second React.ComponentProps - appears to just extract the props of a React component. So:

type ComponentPropsOfTypeofMyComponent = ComponentProps<TypeofMyComponent>; 
//type ComponentPropsOfTypeofMyComponent = {
//    name: string;
//}

Thirdly the & syntax is just creating a type intersection

So for example:

type A = {
   name: string; 
}

type B = {
    age: number; 
}

type C = A & B; 
// type C = {
//   name: string; 
//   age: number; 
// }

Long story short - what that code is doing is saying 'Hey whatever the shape of the props of ComponentA is - and add {someProps: string;} to it'.