Back in the days of 35mm film, a 50mm prime was considered a 'standard' lens. That's because it gives pretty much the same perspective as viewing a scene with the human eye, without the magnification of a telephoto lens or the shrinkage a wide-angle lens uses to squeeze more into the frame.
The flexi disc (also known as a phonosheet or Soundsheet, a trademark) is a phonograph record made of a thin, flexible vinyl sheet with a molded-in spiral stylus groove, and is designed to be playable on a normal phonograph turntable.
Optical drives retrieve and/or store data on optical discs like CDs, DVDs, and BDs (Blu-ray discs), any of which hold much more information than previously available portable media options like the floppy disk. The optical drive normally goes by other names like a disc drive, ODD (abbreviation), CD drive, DVD drive, or BD drive.