network address translation
Usually writing an ip address and a number after the : ,it means the number after the : is  the port

In the internal part:
192.168.0.2 is the private ip address of the host its his ip address inside the network,notice that we have 2 types of ip addresses: private ip address-which is the ip address inisde out network and public ip address which is our ip address in the "internet"
so 192.168.0.2 its the private ip address of the host and the 1234 its the port of the client-the host

now the 42.35.12.33 is the ip address of the web page and the page listens to the port 80

In the external part:
we can see the  ip address of the host has changed,why has it changed?because what i said before about private and public ip addresses this-this ip is the external ip which the host was provided(i suggest reading about NAT if you want to understand this part deeper) the port of the host stays 1234