Receiving two consecutive responses

I found this iRule on another post for logging. Can someone break it down for me in laymen's terms?

 

 

when HTTP_REQUEST {

 

set the URL here, log it on the response

 

set url [HTTP::header Host][HTTP::uri]

 

set vip [IP::local_addr]:[TCP::local_port]

 

}

 

 

when HTTP_RESPONSE {

 

set client [IP::client_addr]:[TCP::client_port]

 

set node [IP::server_addr]:[TCP::server_port]

 

set nodeResp [HTTP::status]

 

 

log connection info

 

log local0.info "Client: $client -> VIP:$vip$url -> Node: $node with response $nodeResp"

 

}