we know ip address is one of the important element in networking
ip address is used to reach destination computer
when we visit a website say googl.com
the isp is configured us a service called dns
dns will convert domain name into ip address
now ip addresss has 2 parts ,one is network address which is used to reach destination network,host address is used to identify destination host within network,in addition to that destination proceess number (port number) used to reach right process ,for web service server listens on port 80, so our destinatiion port is 80,for well defined ports no need to mention port number.

summary:

reaching from our network to other network done in 3 steps
reaching
1.network
2.host
3.process