Most wireless routers can operate as an access point (AP) for clients. Some add other wireless modes that can be used to extend the range, introduce multiple router/access points to the network, or bridge network segments together. Below is a summary of the different modes and their meaning:
AP mode - this is the default, most common mode for all wireless routers, also called Infrastructure mode. Your router acts as an central connection point, which wireless clients can connect to.
Client mode - The radio interface is used to connect the internet-facing side of the router (i.e., the WAN) as a client to a remote access point. NAT or routing are performed between WAN and LAN, like in "normal" gateway or router mode. Use this mode, e.g., if your internet connection is provided by a remote access point, and you want to connect a subnet of your own to it via Ethernet.
Client Bridged mode - The radio interface is used to connect the LAN side of the router to a remote access point over Wi-Fi. The LAN and the remote AP will be in the same subnet (This is called a "bridge" between two network segments). The WAN side of the router is unused and can be disabled. Use this mode, e.g., to make the router act as a "WLAN adapter" for a device connected to one of its LAN Ethernet ports.
Repeater - In general, a repeater simply regenerates a network signal in order to extend the range of the existing network infrastructure. A WLAN repeater does not physically connect by wire to any part of the network. Instead, it receives radio signals (802.11 frames) from an access point, end user device, or another repeater and retransmits the frames to client devices wirelessly. This makes it possible for a repeater located in between an access point and distant user to act as a relay for frames traveling back and forth between the user and the access point. This retransmitting of data typically halves the speed of the connection if same radios are used for both transmissions.
Repeater bridge - A wireless bridge connects two LAN segments with a wireless link. The two segments are in the same subnet and look like two Ethernet switches connected by a cable to all computers on the subnet. Since the computers are on the same subnet, broadcasts reach all machines. DHCP clients in one segment can get their addresses from a DHCP server in the other segment.
Ad-Hoc mode - This is for peer to peer wireless connections. Clients running in Ad-Hoc mode can connect to each other as required without involving central access points.
See Also:
How to set a Wireless Router as an Access Point?How to Secure your Wireless Network
