Input for example is a mouse, keyboard, microphone while an output is a monitor, headset/speakers. an input sends data into the computer while an output sends it out again, hope this helps
Since I have an iMac late 2013, I can tell you what is on a mac. There is a Headphone port, a Microphone port, a Firewire port (WORST PORT EVER), the 3 USB ports (The Most Useful), the Ethernet port (If you are close to an Internet box you can plug in; somewhat useful!).
2. The input is when you plug something in that provides something for the computer (headphone, microphone, USB etc). The output is when the computer provides something for you (sound, files, websites etc).
