load sharing can be defined as:
the use of 2 or more links to provide multiple access paths from a source to a destination; with load sharing, one link could handle 20% of the traffic while another link handles 80% of the traffic; load sharing does not constitue load balancing; the load is shared among multiple paths, it may not be balanced.
ie: load sharing can be seen alot in bonded BRI links. when 1 BRI reaches a specific utilization threshold, you can have the router dial-up the second BRI to share some of the load.
load balancing can be defined as:
the use of 2 or more links to allow for the 'balancing' of traffic among them.
ie: packet based balancing - the first packet is sent down the first link; the second packet is sent down the second link; the third packet is sent down the first link...etc.
destination based balancing - traffic destined for one 'destination host/network' is sent down the first link. traffic destined for another destination host/network is sent down the second link...etc.
(these terms do seem to be interchanged as general industry terms but i do think it is correct to note there is a difference)
