HTTP(S) load balancers are the most popular and most widely used, simply because there is so much that can be done at this layer. It is possible to distribute traffic based on the type of incoming request; for instance, requests for static content go to one set of servers, while requests for video content go to another. This is called content-based load balancing.
It is, of course, most common to simply route requests to the nearest backend servers that can field a request; if those backend servers reside in different regions, then this is called cross-regional load balancing. This is something that can be used, for instance, to direct traffic originating in India to servers that are also located there.
HTTP/HTTPS (commonly written as HTTP(S)) load balancers deal with HTTP requests on the instances. They support both IPv6 and IPv4 traffic from clients. The...