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.