SSL termination is the process of decrypting traffic before it's passed on another server such as Access Gateway. When used with a load balancer, SSL can be terminated at the load balancer or encrypted traffic can be passed directly to Access Gateway and SSL terminated there. See Load balancers.
Which method is selected is largely a matter of preference. When SSL is terminated at the load balancer then decisions can be made about the traffic based on the information itself. Sophisticated load balancers provide such functionality. Often its a benefit to the back end server to terminate SSL at the load balancer. For example to conserve CPU performance and then not requiring decryption by the back end. However with Access Gateway all traffic between Access Gatewayand the load balancer uses HTTPS and is encrypted for security purposes negating this benefit.