I see this forum's shall provide lots of fast and useful help for novice users ...
I found it by myself - here it is, in page 32
• The device forwards all network management and data packets from one network interface to the other without any intelligent routing. For simple applications, this provides an efficient and fully transparent network solution.
• There is no network segmentation, and the broadcast domain is the same. Bridge mode does not block any broadcast or multicast traffic. You can configure additional firewall settings for Layer 2 packet filtering and access control.
• WLAN and LAN interfaces belong to the same network segment and share the same IP address space. They form the virtual bridge interface while acting as bridge ports. The device features IP settings for management purposes.
• The device operates in Layer 3 to perform routing and enable network segmentation – wireless clients and the WAN interface are on a different IP subnet. Router mode blocks broadcasts and can pass through multicast packet traffic. You can configure additional firewall settings for Layer 3 packet filtering and access control.
• The device can act as a DHCP server and use Network Address Translation (Masquerading), which is widely used by APs. NAT acts as the firewall between the LAN and WAN.
• For example, Router mode is used in a typical Customer Premises Equipment (CPE) installation. The device acts as the demarcation (demarc) point between the CPE and Wireless Internet Service Provider (WISP), with the wireless interface of the device connecting to the WISP.