ConfigureServices and Configure methods in Startup.cs of Asp.net core

Sample Startup.cs

// This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit http://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {

            services.AddMvc();
            services.AddSingleton<IDataService, DataService>();
            services.AddSingleton<IViewModelService, ViewModelService>();

        }
        
        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app)
        {
            app.UseIISPlatformHandler();
            app.UseMvcWithDefaultRoute();
            app.UseStaticFiles();
            app.UseStatusCodePages();
        }