Laravelのガードとは何ですか

/*
    | Authentication Guards
    |认证关卡
    | Next, you may define every authentication guard for your application. Of course, a great default configuration has been defined for you here which uses session storage and the Eloquent user provider.
    |接下来，你可能要为你的应用定义每个认证关卡。当然，已经为你定一了一个很不错的默认配置。这里会使用会话储存和用户模型
    | All authentication drivers have a user provider. This defines how the users are actually retrieved out of your database or other storage mechanisms used by this application to persist your user's data.
    |所有的认证驱动都有一个用户提供者。这里定义了怎么实际上怎么从你的数据库或者其他储存机制中取出用户。以便应用开保持你的用户数据
    | Supported: "session", "token"
    |可选驱动："session", "token"
    */
'guards' => [
        'web' => [
            'driver' => 'session',
            'provider' => 'users',
        ],
        'api' => [
            'driver' => 'token',
            'provider' => 'users',
        ],
    ],

  /*
    | User Providers
    |用户提供者
    | If you have multiple user tables or models you may configure multiple sources which represent each model / table. These sources may then be assigned to any extra authentication guards you have defined.
    | 如果你有多个用户表或用户模型，你可以配置多个代表用户表或模型的资源。这些资源可能被分配给应用中你定义的其他认证关卡
    | Supported: "database", "eloquent"
    |
    */
 'providers' => [
        'users' => [
            'driver' => 'eloquent',
            'model' => App\User::class,
        ],
        // 'users' => [
        //     'driver' => 'database',
        //     'table' => 'users',
        // ],
    ],

  /*
    | Resetting Passwords
    | 密码重置
    | You may specify multiple password reset configurations if you have more than one user table or model in the application and you want to have separate password reset settings based on the specific user types.
    | 如果你有多个用户模型或表，并且想对不同用户类型有特定的密码重置，则可以配置多个特定的重置密码
    | The expire time is the number of minutes that the reset token should be considered valid. This security feature keeps tokens short-lived so they have less time to be guessed. You may change this as needed.
    |这个获取时间是令牌过期的分钟数，这个安全措施可以保证令牌保持段时间有效，因此有更少的时间被破解。你可以按照需要更改。
    */
    'passwords' => [
        'users' => [
            'provider' => 'users',
            'table' => 'password_resets',
            'expire' => 60,
        ],
    ],

  /*
    | Authentication Defaults
    | 默认认证配置
    | This option controls the default authentication "guard" and password reset options for your application. You may change these defaults as required, but they're a perfect start for most applications.
    | 这个就是应用的默认认证关卡个重置密码，你可以按自己要求更改。但这是最适合一个新应用的配置
    */
    'defaults' => [
        'guard' => 'web',
        'passwords' => 'users',
    ],