After years of using passive FTP I figured I should find out what it actually does compared to Active FTP.

The difference is in Active, your client tells the server what port you will be doing your business on.  Active has worked fine for years, usually on port 21. However with more and more firewalls there had to be a different way. This is where passive mode comes in. In Passive FTP, the client asks the server what is the best port for the server to use. The server responds with a non-blocked port and you can go ahead and transfer.

As a note, in my experience with ftp, if you are getting errors trying to connect. First check all the host/login information.  If that is all inputted correctly its a pretty safe bet you need to use passive ftp.