PPPoE stands for Point-to-Point Protocol over Ethernet. It is a non-standard method of connecting to your ISP to gain a dynamic IP address. It relies upon a software client that is provided by the ISP. A dynamic IP address is required to gain a connection to the Internet.
[Cited from Wikipedia] In the context of computer networking, Dynamic Host Configuration Protocol (DHCP, currently implemented as DHCPv6) is a client-server networking protocol. A DHCP server provides configuration parameters specific to the DHCP client host requesting, generally, information required by the client host to participate on an IP network. DHCP also provides a mechanism for al
NAT stands for Network Address Translation. It is proposed and described in RFC-1631 and is used for solving the public IP address depletion problem. At present, many Routers support this NAT function. The NAT box can "translate" the local IP addresses to global address and vice versa. In other words, it is a method of connecting multiple computers to the Internet (or any other IP network) using one public IP address.