Questions about ports in networking.

[Supra]

So applications can use those ports instead of other apps running a port that you need. Server based stuff needs alot of open ports

[Chad]

What is the purpose of opening ports in your router?
Why would we want to open certain ports? like 21, 25, 80, 443, 3074, 32285?

21 is for FTP.
25 is for Email Authentication.
80 is usually used for TCP for Webbrowser, Home Servers, etc etc...
443 is for HTTPS. S being for Secure.
3074 is for Xbox Live. Never knew that until now, thank you.
32285 is usually for Torrents.

Basically if you Port Foward, you are allowing a certain program to access that port to your computer/console at any given time without having to open it etc etc making it faster to use.

If you want to use TCP or UDP for a program such as a RAT (Remote Administration Tool) you would have to use a port, normally not in use in which you can make your program check for.