Typescript 里的这种写法是什么意思？

在看源码的时候发现下面这种写法，不明白是什么意思，请教一下各位：

const temp: ToughCookieFileStore = {
    [domain]: {
        [path]: {
            [name]: {
                key: name,
                value: etcCookie.value,
                expires,
                domain,
                path,
                secure: etcCookie.secure,
                httpOnly: etcCookie.httpOnly,
                hostOnly: etcCookie.hostOnly,
            },
        },
    },
};

下面是接口的声明

 export interface ToughCookieFileStore {
  [site: string]: TCFSPaths;
}

export interface TCFSPaths {
  [site: string]: TCFSCookies;
}

export interface TCFSCookies {
  [cookieName: string]: TCFSCookieAttributes;
}

export interface TCFSCookieAttributes {
  key: string;
  value: string;
  expires?: string;
  maxAge?: number;
  domain: string;
  path: string;
  secure?: boolean;
  httpOnly?: boolean;
  extensions?: string[];
  hostOnly: boolean;
  creation?: string;
  lastAccessed?: string;
}