system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come the same computer that runs a complex game like Battlefield 3 at high fps can lag when using simple programs like iTunes?
gpt
Game Developer here -- Your computer is made up of many parts, and different programs do very different things. Your video card's GPU has nothing to do with your hard-drive, and people who make video games avoid reading from the hard drive as much as possible as thats generally the slowest possible operation on a computer.

An application like iTunes may read from your hard drive, make slow (blocking) network calls, connect with other devices etc. It may be doing "less complex" things but its doing it with different hardware. 

Also, some programs are written better than others :)