Web API 2 OWIN Bearer令牌的目的是什么？

我试图了解MVC 5中单页应用程序模板中新的OWIN Bearer Token身份验证过程.如果我错了请更正我,对于OAuth密码客户端身份验证流程,承载令牌身份验证通过检查http授权请求标头来工作对于承载访问令牌代码,以查看请求是否经过身份验证,它不依赖cookie来检查特定请求是否经过身份验证.

根据这篇文章:

使用Web API示例进行OWIN承载令牌认证

public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
{
    using (IdentityManager identityManager = _identityManagerFactory.CreateStoreManager())
    {
        if (!await identityManager.Passwords.CheckPasswordAsync(context.UserName, context.Password))
        {
            context.SetError("invalid_grant", "The user name or password is incorrect.");
            return;
        }

        string userId = await identityManager.Logins.GetUserIdForLocalLoginAsync(context.UserName);
        IEnumerable claims = await GetClaimsAsync(identityManager, userId);
        ClaimsIdentity oAuthIdentity = CreateIdentity(identityManager, claims,
            context.Options.AuthenticationType);
        ClaimsIdentity cookiesIdentity = CreateIdentity(identityManager, claims,
            _cookieOptions.AuthenticationType);
        AuthenticationProperties properties = await CreatePropertiesAsync(identityManager, userId);
        AuthenticationTicket ticket = new AuthenticationTicket(oAuthIdentity, properties);
        context.Validated(ticket);
        context.Request.Context.Authentication.SignIn(cookiesIdentity);
    }
}