What is packet forwarding?

Packet forwarding in simple terms is the forwarding of packets from one node to another from networking point of view. For example, a router or a switch. These networking devices make routing devices with the help of their routing tables and then select an outgoing interface. After that they make some changes in the packet header and push (forward) the packet to the selected interface.

In case you don't know the meaning of packet. Packer is the smallest unit of size in networking. Different networks has different packet size. For example, in ATM Networks the packet size is of 53 Bytes.