They both have the same effect: your website loads faster. However, they work in different ways. Autoscaling ensures that when your website gets busy, it has access to as much resource as it needs, so it doesn’t slow down. A single site can take advantage of a whole server or many servers.
Load balancing stops other busy websites on our shared platform having an effect on yours. It balances the traffic load between multiple servers. It also works as a safety measure: if in the unlikely event of a server failure, it can ensure that your site stays online.