angular.module("mainApp")
    .config(function ($stateProvider, $urlRouterProvider) {
        $stateProvider
            .state("a", {
                url: '/a',
                templateUrl: 'app/a/a.html'
            })
            .state("b", {
                url: '/b',
                templateUrl: 'app/b/b.html'
            })
        
        
app/index.html:


....
<p ui-view></p>
....
        

ui-router is through the position of state进行页面跳转控制的，具体来说，当一个页面加载了ui-router及其相关router配置后（上面的示例代码），会跟据地址栏的url加载对应的模板，比如上文，如果访问了/a这个路径，ui-router会知道这个/a路径对应a这个state，他的模板是app/a/a.html，之后就会加载这个模板，并把它塞到ui-view这个directive (this may not be very appropriate, because state can be inherited and views can also be nested, which is a far stretch)

It is recommended to take a good look at the ui-router wiki