The generic difference between loadbalancer and Failover is :
In case of load balancer, traffic is routed to more than one (2-3 or more) sites,nodes or network elements to have an equal sharing of incoming traffic. This is achieved by filtering traffic on the basis of subscriber type, location type etc. At a time all the sites are active and handle the traffic.
While in case of Failover, the primary node handles the traffic and secondary is (in healthy status) acts as a redundant node. In case of primary node - failure, or disconnect, the secondary becomes active and starts acting as traffic-handler.