There two different ports are there.
First one is Physical Ports that are used to connect two different hardwares. It will available behind your CPU. The different types of physical ports :
Using the physical ports only, we connect the Keyboard,monitor,Mouse,Modem to your CPU.
Second one is Virtual Port
We know that physical ports used to connect two hardwares. Likewise , Virtual ports are used to communicate two different applications. Virtual ports are part of TCP/IP networking.
Computers and routers automatically manage network traffic traveling via their virtual ports. Network firewalls additionally provide some control over the flow of traffic on each virtual port for security purposes.
Port is a Virtual path to send and receive data from computers. Like a door in a house. We use the door to go inside home(computer) and come outside right.
A house can have more than 1 door , right? Yes computer has about 65535 doors(sorry ports). In real world, you will name the door as front door,backdoor. It is hard to remember the 65535 doors name so it is better to use numbers(like 1st door,2nd door....65535th door). Each door must have some purpose right? Likewise , Each port has some purpose. Various ports and their purposes
HTTP : 80
SMTP : 25
POP : 110
Telnet : 23
NetStat : 15
Ping : 7
Systat : 11
Time : 13
Whois : 43
SSH : 22
Finger : 79
A software which runs on a port is called service.
There are two status for ports namely open and closed. In home , you can enter if the door is open right? you can enter into house ,if it is locked. Likewise you can use opened ports only to connect to the computer. Usually we left our front door as opened. Likewise , computers has also around 5 ports as opened.
In order to find opened ports, you have to search for it. You can use some kind of batch program to scan ports or you can use Port scanners